Slurping and Vomiting

Okay, so, FTM here. My BF 5 week old has always spit up more than 2 tablespoons of his feeding (basically vomited most times after feeding). He was on Zantac for a 1-week trial that didn't help at all. He is burped every time. I've gone as far as burping after 5-15 minute intervals during feedings. I've cut out dairy for a trial, but that didn't seem to help. We also hold him upright for 20-30 minutes after nursing.

In the past 2 weeks, though, he's had a handful of episodes where he has thrown up almost all his meal (curdled and milky breastmilk).

In only the past few days, I've noticed he's been slurping more during feeding (I relatch him as often as I can)...could it be overactive letdown?

My question is, would any of this vomiting be contributed to taking in too much air while feeding? I know he's probably going through a growth spurt, as well, so that could aggravate things. Him straining to poop also seems to make his vomit worse. I can tell the reflux bothers him, because he cries a bit when it's coming up. His gas is noticeably louder in his tummy, as well. Wondering if i should continue the dairy-free diet and also cut out, acidic foods and soy, as well...