my dd had chronic reflux, she ended up in hospital a couple of times as her oesaphagus was so inflamed,
you have probably been told most of stuff but i found when i was bf the best position for her was in the rugby hold one and she was quite propped up on pillows so she was almost upright, the hospital suggested it would be more comfortable for her if i fed her upright, also had to keep her upright for at least 2o mins after a feed which was a bit of a pain in night feeds!
feeds were easier to keep down if she had small feeds more often, she kept the feed down better if she was fed every hour to 2 hours rather than 4 hourly - apparently the trick is to not let them get hungry as that increases the acid in their stomachs
presuming you already have his mattress raised at an angle, i also put her to sleep on her tummy against all the advice i know but it was the only way she would settle and the hospital were fine with me doing that
i also had to wean her at 17 weeks however this was on the advice of a paeditritain as she was not putting on much weight
hope some of this helps, cant beleive it has taken you so long to get a diagnosis it took me 6 weeks and i thought that was bad!
but it does get better the bigger they get, she is nearly 3 now and it hardly affects her unless she gets a bit over excited after eating and she can tell me when her tummy hurts so i can give her the gaviscon
good luck x