One I really think you need to slow down and let him adjust to each formula first you have tried WAY to many in such a short time. This is not good for him at all!
Two is there a reason why you are not breastfeeding...you have not said...it is not to late to start or restart! Especially if he is having this problem.
Three Neutragama? Very expensive but is a good option.
Four Chiropractor Seriously try it it will not hurt him! Our son was so tight in his chest area and that was what was causing his reflux!
Five how much is he really spitting up...if he is gaining weight he is fine. Yes it may be annoying and less convenient for him to spit up but some babies do this!
You really need to stop...asses the situation better before you change things up even more! Get pumping and make some breast milk for him if you can that is the all time best. Understandable if that is not possible but please PLEASE rethink this constant changing of formula this is not good for him at all!!!!!!!!!!!!