J.C.
So it sounds like you are doing everything medically that you can.
My only suggestion is that you take him to a really great osteopath. They can really work wonders with all types of medical conditions.
I took my daughter at 3 months old after she had been screaming non stop for the first 3 months of he life, innacurately diagnosed with colic, acid reflux...etc. After her first appointment she stopped screaming!!!! no more colic!!!
I took her again at 1 year old because she developed a weird type of crawl "the army crawl" we called it... (one leg behind and other crawling) but she crawled normally within 2 days of her next osteopath appointment.
We were absolutely amazed with each visit!
I know these are both different than your situation, but i hope that an osteopath may help your little one as well,
Good luck and I really hope that all is well with your boy.