I have no words of wisdom, but I know I've been in your shoes with my family. I raised 5 kids and I know how much kids especially growing boys eat. Here is what I did when faced with the same situation you are in:
Make a weekly menu and post it on the frig.
When and believe me the food designated for the menu will disappear that night you fix P & B sandwiches and chicken noodle soup. This is the tough part......fix it serve it with no blaming no animosity just eat. The culprit gets the picture and his brother and sisters will put the pressure on the culprit for ruining an otherwise good dinner.
You will have to do this several times, reaching into the back of the cupboard to find something else to eat, and don't substitute the next nights dinner with the one missing. If the next nights is also missing so it goes......one night we had left over cereal ( the icky stuff no one eats) with powdered milk and there was just enough for each of us to have one bowl which left us all hungry. All the kids complained all night that they were hungy and the piggy kid got the picture. I did pop some pop corn, lots of it and good thing it expands in your tummy, LOL.
You need to give him some other options to eat stuff to fill him up, keep fruit, cut up veggies, pop corn (note healthy choices) in good supply and let him and the other kids know they can eat unlimited quantities of it but to lay off the stuff designated for dinners. Whole grain breads can be bought at bread outlet stores for a buck a loaf and these are great for filling them up and good for you. Buy the biggest jar of natural (not Jiffy) peanut butter and some lower sugar jelly this is a healthy filling snack.
Soda is crap I agree no one needs to drink it, milk is crap too. Get them used to fruit juices and dilute it. I buy unsweetened cranberry juice and from a quart I can make a gallon. It actually quenches your thrust and is good for you.
Being hypervigulant about food creates more hunger and also eating disorders, trust me on this one! My oldest daughter had bulimia talk about a waste of food......talk about a lot of $$ spent on therapy! You can afford the healthier food way more than the $$ for therapy!
You made a comment about not being able to afford the healthier foods well I don't agree with that. It takes time to adjust to eating healthy but after a couple of weeks your body adjust and you actually quit craving the crap food. Actually for me it only takes 3 days and my food bills are lower when I eat whole live foods and limit my meat to chicken, fish and lean cuts of beef eaten just a few times a week not daily, the meat that is.
Purge all the crap food from your house, anything white is crap! LOL No white foods!
......steps off my soap box
Good luck and you're only normal to feel the way you do, change your attitude, change the diet and it will make a world of difference on everyone.
PS My daughter who had the eating disorder......she has two kids and lives by the above no white food and boy does she scold me when I try to give my grandkids sugary foods! Hey the grandkids even scold me they don't like sugary foods! No cookies in my cookie jar when they are here, just a nice big fruit bowl and tiny boxes of raisins, they love 'em! I had to realize I was doing to my grandkids what my granny did to me baking homemade treats, sigh. Now I just love 'em up and play with them they crave the attention more than the food. Ahem......maybe your son needs more attention in a positive way?