splendide - It shouldn't be a fluke. The more milk he has, the better he will sleep because he's not hungry.
sazzlehopes Are you anywhere near the 12 week growth spurt? Give it a few days, a week most, and hopefully things will improve on their own.
Bump If baby is gagging and being sick on the teat, sounds like the flow might be too high? Breastfed babies tend to stop on the level 1 teat size with slower flow. Also makes baby suck harder from the bottle teat, like a breast.
Tatty/Fed/Bump- I assume you've tried altering temperature? Some babies like it room temp, others hot, others cold. My DD likes hers hotter than expected (40 to 50 secs in microwave for 6oz of cold milk - I know The Rules say you shouldn't microwave milk, I'm a rebel)
Also doing it when baby is half asleep and not hungry at first
Something else I found that worked to get baby used to the bottle was breastfeeding first, then positioning bottle while still breast feeding and whip nipple out of mouth and slip the bottle teat in really quickly. I kept baby with the breast and at any upset swapped back to breast and back to bottle again. This isn't a plan for the long term, but helpful to first get baby used to the bottle.