I was given Osmolite and added 8oz of water to thin it out. Also used a gravity bag to feed with as opposed to the syringe. Slow and steady was key, usually 20 minutes or more to empty the bag. Too fast and I got sick. Definitely check about the formula and try thinning it and the gravity bag.

I don't know what to tell you about sleep as I had the opposite issue and couldn't lay prone on the bed. I had no choice but to sleep sitting in a recliner and did so for a couple of months. I bought one of those neck pillows (for air flights) that helped my neck. Sleep was more like 1-3 hour naps for a long time. Eventually you'll sleep if even just naps.

Positive thoughts and prayers