I’m simply speaking anecdotally. I’ve had good success with crunches with no pain or lingering discomfort. Standard crunches, decline crunches, weighted crunches and twisting crunches are all still included in my ab work today. Crunches are not the main builder of abdominal muscle, they are good complimentary exercises to heavier core exercises. Yes, they are isolation exercises. But isolation exercises have a role in an effective muscle-building program.
Yeah, no need (or likely much benefit to) all that sort of stuff. Beef, pork, chicken, fish, salad, etc.are all fine. A mix of protein, complex carbs, and healthy fats, avoiding the simple added sugar style carbs and highly processed foods. If you want to add mass you do need more calories. Likely you will get hungrier as your body responds to exercise and you don’t need to overthink it too much.
“Ideal” nutrition can be another large number of answers all of which work well. Minimal amount of protein should be 0.8g/kg/d (not of “meat” but of the protein; even meat is not pure protein) and some go significantly higher, even up to 2.0g/kg/d. Greek yogurt is pretty protein dense.
Unclear really how vital timing is but the standard advice that I still believe makes sense is that it is best to have a complex carb snack an hour or so before a major work out and a higher protein one within an hour after it. If anyone could benefit from that approach someone like you might.
At the level you are talking about 100% it will be as effective to do things all in a single day and you are, sorry, indeed 100% wrong. Your individual muscles can only put on so much mass at a time, but all can do it at the same time.
The logic for splitting work outs (or skipping days between significant complete body resistance training) is to give recovery time to the muscle groups. Minimally that helps reduce injury risk and may even increase the ability of the muscles to respond to the stimulus. That applies more to significant resistance work than to aerobic work (although it applies to especially hard aerobic work too). Thus the standard approach of alternating resistance work days with aerobic focused days for overall fitness.
Ambi probably isolation exercises are not what this person needs at this point.
Do Pilates. Have you ever seen a picture of Joseph Pilates? He was ripped!
interesting site Soylent Juicy shared: I was expecting them to try and sell me something but all that info is free. thumbs up
here is a link to more exercises you can do without equipment Essentrics
originally this woman (in her 60s) had a PBS exercise show called Classical Stretch. she has TONS of DVDs you can buy, you can get them free at the library, or you can just do the mini workouts at the link. She has done two programs PBS uses for pledge drives Aging Backwards and Forever Painless.
give it a try 
You may want to consider seeing a doctor again, or ask for a referral to a specialist about your lack of appetite. Lean proteins and veggies are good, but it seems like you may be undernourished.
As** DSeid** said, unless you’re doing serious strength training you don’t need rest days. Your muscles need time to repair but you’re not ripping them down like you would if you were doing more than bodyweight exercises.
Your anecdota is contadicted by the almost uniform opinion of exercise physiologists and atheletic training organizations. There are many exercises that work the rectus abdominus that are of greater overall benefit and do not pose the risk of injury that crunches do. The notion that crunches help target belly fat reduction or provide some particular benefit over more functional compound exercises has been long debunked.
Not to detract from the Pilates exercises which is an excellent system for prehabing and developing the core muscles and protecting the lower back from injury, but Joe Pilates didn’t exclusively do Pilates exercises and you won’t develop the all around musculature he had just from Pilates exercises.
As others have noted, there is no need to do ‘splits’ of muscle group exercises unless the o.p. is overloading (working muscles to exhaustion or maximizing single rep lifts). The purpose of doing splits isn’t because of any competition for nutrition between muscle groups or anything like that, but to allow for more recovery time per worked muscle groups while maintaining a high volume of work. If the o.p. is not engaging in overloading–and there is no good reason to do this and a lot of reasons not to unless you are on a program for competitive lifting or bodybuilding–then there is no reason for multiday recovery periods. Depending on the volume of work, he may want to alternate days of high:low:moderate volume or maximum effort, with one or two days of ‘active recovery’ (just walking or other light exercise) per week. Basically, moderate exercise on sequential days to avoid straining muscles or being in constant fatigue and pain which is counterproductive and can lead to injury through overuse or adverse compensation, as well as just not being an enjoyable way to live or building a habit of regular exercise.
Stranger
One challenge for the beginner is, as you know, you’re not sure of what to do, how to do it, and how often to do it. One great way for a beginner to start exercising is to join some group fitness classes. You will work out under the guidance of a professional who will help you maintain proper form, avoid injury, and can give you specific advice for your goals. There are a wide variety of classes for different fitness levels and types of workouts. Some classes will be dance based, others will use weights, others will be based on fighting sports, etc. Even if the group environment isn’t your preference, consider it as a beginner. It is like going to driving school before you get your license. It will give you the knowledge and solid foundation to exercise in other ways as you get more advanced.
Some group classes are standalone–such as morning boot camp–while most others are taught in a gym or studio. I would recommend joining a gym since they typically have a wide variety of classes included with your membership. Large, national gyms will probably be your best bet since they will have more standardized versions of classes. Find a gym that offers month-to-month memberships rather than year long so you’ll have flexibility as you’re starting out. In terms of the cost, look at it as the tuition for going to exercise school. You may only need to pay it for a few months and then you can go off and do your own thing.
For you specifically, I would recommend you look for these types of classes:
BodyPump – A weight-based aerobics class. An all over strength class. You use a bar with however many plates you need for your workout.
Kickboxing-type classes–Aerobic and core strength class. Lots of punching and kicking moves.
If you decide to try group classes, tell the instructor you’re a beginner and find out if there are any modifications you should do. You’ll want to work out very easily the first few times to give your body time to adapt. If you work out at full speed from the first day, it’s easy to get injured.
Stranger I’m no fan of crunches but your ACE link does not call up the article and on their site what I find instead is this inclusion of crunches as a beginner exercise and directions on how to do them, and this one ranking exercise ball crunches as one of the very best ab exercises, up with the bicycle maneuver, and the captain’s chair. Okay the traditional crunch was not in the top.
OTOH I have no idea why they (allegedly an expert organization) think specific targeting of the abdominal muscles is such a desired thing.
It’s a bit hyperbolic to claim that there’s “almost uniform opinion of exercise physiologists and atheletic training organizations” on the evils of crunches … but agreed there is potential to do them poorly and lots better to do. Agreed with your bigger point that functional compound exercises hit the abs fine and that thinking of abs in isolation is silly (excepting perhaps for a competitive bodybuilder like Ambi who also already has very low body fat at competition assured).
OP -
You asked about nutrition.
I’m not going to make a blanket statement, and say they anyone who wants to put on lean muscle mass must eat this, but a staple of my routine is Fage noon-fat Greek yogurt. I eat it every day with Kashi Go-Lean cereal, and whatever berries I can find. It’s an excellent source of protein without a lot of fat. Nuts (Almonds, esp.) are also good as a snack, instead of something like a piece of candy of a cookie.
Our other staples are ground Turkey and various fishes (Salmon, tilapia, etc.),. prepared very simply. My wife typically makes Brussel sprouts or cauliflower roasted in the oven with the fish.
Up until last year I was eating very little meat, but my training partner loves to go the the local Korean BBQ, so I’ve added meat back in once a month or so.