Obligatory pic of Oscar blissed out on nip
So, I need help figuring out how to keep the little rascal from a) jumping on the counters and b, c and d) using loaves of bread, rolls of paper towels and the cables of my surround sound system as chew toys. Ideally, I’d like something that will curb these behaviors “right now” and that will be working while nobody is home
For the counters you need:
To stop the chewing, bitter apple spray:
And spray bottles in every room in case you bust him in the act.
Put the paper towels and loaves of bread out of his reach (in a cupboard?). Wrap the cables in aluminum foil. You can try a product called “Sticky Paws” on the counters if you have granite or something else the sticky won’t hurt; it’s basically double-sided tape and cats hate the feel of it on their paws. For the same reason they leave aluminum foil alone. Then you might set up a camera so you can see what he does when you’re gone. Our cats mostly sleep when we are gone so they don’t get up to much, but they’re older.
I really vote against the things recommended by SmartAleq as they are things which have failed for us and which are expensive. I also recommend that you spend as much time as you possibly can playing with Oscar and otherwise interacting with him, as a tired sleepy cat is a good cat.
I think the key is working with the cat’s instincts, not against them. Give them toys that are the shape of the paper towel rolls and loaves of bread, for instance, since they seem to like to “kill” those shapes.
Well you sure can’t look at that picture and say “he needs more toys”. Lol.
To sum up the previous replies, the key is to manipulate the cat’s environment to make the problematic behaviour naturally unpleasant. Many (most?) cats have no notion of good-vs-evil or even of reward-vs-punishment, so spraying them with water when catching them in the act may be satisfying for humans but doesn’t always induce long-term improvement.
Try Feliway.
Agreed, the cans of air spray cost to much. You can use cans of computer spray in place but still they are a pain to keep using for long.
I let my cats on one counter and place an empty Amazon box on it, they sit on top of it most of the time as the generally just want to be up on my level.
Probably easier to adjust your expectations 
“Probably easier to adjust your expectations”
Agreed. I just put things away safely and avoid having anything fragile in a vulnerable position. I have my doubts that you can discipline cats, so just make your house as cat-proof as possible.
Deterrent sprays are better used outdoors, do you really want the residues in your house?
Place set generic mousetraps on your counters, then carefully place a sheet of newspaper over the traps. If the cat hops onto the counter, the traps will scare the bejesus out of him. Some people remove one spring from each trap, making them less dangerous.
A safer and simpler suggestion I’ve seen is placing easily knocked over aluminum can arrangements on counters or tables. When the cat jumps up, it makes a disagreeable racket. Like a light baking sheet with a tower of cans on it set near the edge.