Likewise I've been lurking and so glad to see that it's a situation you can get a handle on and happy to move forward with!
While none of my boys have had birth defects, all their special needs have emerged later and largely due to their prematurity etc, my youngest got hit with a rare complication of his feeding tube surgery which resulted in incredible pain for him.
I know you had concerns about a life of pain for your wee man so I'd really like to reassure that kids are incredibly resilient too and often watching the pain is harder than living with it (I have arthritis and so can see the other side as well!).
That's not to belittle the pain kids can go through - and it broke my heart the time T said to me "Sometimes I wish I hadn't been born because then I wouldn't have got the gloopies" - that's what we called his GI issues as he made a glooping noise when he ate or drank.
There were times when he said he just couldn't bear the pain anymore and just couldn't take this. But there were also times when he'd be moving slowly and carefully and I'd ask if he was okay and he'd say "Just sore Mummy, just ordinary sore though not really sore."
He is a happy, outgoing, cheerful, social, chatty boy of 6 3/4 yrs now despite nearly a year of pain we were on the verge of medicating with heavy duty painkillers. That's on top of such severe reflux pain for his first nearly 4 yrs of life that we'd never heard him belly laugh from sheer pleasure until after he healed from his reflux surgery!
A lot of the management is in our own attitudes as parents - and you've very clearly got that one well and truly sussed!

in your journey!