congrats! dd2 doesn't have ds, but had similar issues with her cp (she was born without a gag and swallow reflex, and so was ng fed initially, and then gradually moved to ebm with associated aspiration and choking etc).
if you don't have one, ask to be referred immediately to a speech and language therapist who is a feeding specialist. ours literally kept me sane for the first two years, and i swear is the only reason that dd2 eats orally now. 
fwiw she ended up back in hospital at 6 weeks as she completely stopped feeding, and i've lost count of the number of times i ended up at the gp in tears because she wouldn't/ couldn't feed, but to look at her now you wouldn't believe it. they would just send me to the hospital, as they were terrified of her.
(on the bf side - i managed to get dd2 latched once, at 5 weeks, but her suck was really too weak and i didn't ever manage it again. i had a lot of advice re using supplementer etc, and if you are interested then the nct breastfeeding helpine will put you in touch with very knowledgeable folk about bf with disability and associated issues - but in the end i chose to continue to use a bottle.)
good luck though - you sound as if you are doing very well! (and certainly saner than i was at the same point!)