Wow! You weren’t kidding about working out! You need to come to America. I was picturing a typical factory job here. You work harder in the morning than people here work all week. I don’t think there’s very many jobs here which involve nearly that amount of physical labor on a regular basis.
With a BMI of 19 and working that hard, you need to be eating a lot of calories anyway. Make sure you are getting protein with all your meals. It sticks around for a while. You can also do things like snack on jerky or eggs throughout the day. That will ensure your body has available protein when it needs it.
You’re going to want to listen to your body. That level of exertion can make it hard to keep down a large meal (and large meals can make you tired), and it does sound like you’ll need a lot of calories to keep up. Small meals or snacks throughout the day might be the way to go. But if whatever you’re doing is working for you, then it’s working.
One thing you might want to consider snacking on throughout the day is trail mix. It’s a mix of nuts and dried fruits like raisins and cherries. It will provide plenty of carbs, fats, and protein, and it won’t spoil. People often use it for all-day activities like hiking, and it would probably be good fuel the kind of work you’re doing.
Some of these debates get to angels dancing on the head of a pin level.
Let’s prioritize.
Adequate hydration and real food calories. Listening to your body’s cues should do the job there better than calculating it out but have snacks that are a mix of carbs and protein and plenty of water available as breaks. Yes you will end up eating more calories than you literally burn because some will be being used for repair and for building. But bodies do a pretty good job of getting the brain to get the food that is needed in.
Adequate total daily protein. You’d make gains if that was 15% of your total calories and maybe a bit more if you went higher, like 25%.
If you have meals and snacks that have real food sources of protein in them you’ll have enough protein around to provide both for the synthesis (creation) of new muscle mass (anabolism), and for preventing the destruction of muscle mass for energy and other repair processes (catabolism). Real foods have some protein that gets absorbed quickly and some that takes hours to be absorbed. A good example is dairy, which has fast to be absorbed whey and slow to be absorbed casein.