Well, I'm a meanie and I would pick something that agrees with him and stick to it.
Especially since his energy and poops are good. I think the upset tummy part is real for him, but I also think he's has gotten in to the habit of playing you so you have a vicious cycle of him getting maybe a tiny tummy twinge but out of habit he makes it worse with his food games.
I would stop trying to 'make' him eat. You're stressing yourself (and him) out worrying about him missing a meal. He's a healthy boy, clearly not emaciated, a missed meal isn't going to hurt him other than you'll be up cleaning up bile pukes. Healthy dogs bile puke, it's okay
For the empty tummy pukes, I'd get some good quality dog treats and offer one of those right before bedtime as part of his routine (so he doesn't associate it with meal times and you getting him to eat). Something like this:
https://www.hollywoodfeed.com/p/65414/hollywood-feed-pennsylvania-made-dog-treat-turkey-burgers
It's real food, limited ingredients, good for him, and he'll probably love 'em. If he doesn't eat his, offer it to Sox and give him nothing. If he has any type of FOMO you'll only have to give his refused treat to Sox once or twice before he figures that game out.
Do the same with meals. Offer him his regular food walk away. Ignore him. After 10 minutes, pick it back up and that's it until the next meal time. Remove all the drama from meals that you can. Meals should be food down, let him eat in peace (or not eat, but you don't participate at all either way), and then bowl gets put away.
Keep giving him the antacid. That will help somewhat with the bile pukes, but you'll likely have some unsettled nights, try not to stress. Keep reminding yourself that he's healthy and energetic.
I'd give it about 3 weeks of a no-drama food routine and see if that makes any difference in his willingness to eat at meal times.
Once you get him eating reliably, I'd be tempted to feed just one food and see if that helps at all.