Lots of little babies don't like baths. It's cold, it's shocking. It'll get better with time. Until then, just be quick. It should only take a few minutes to bathe a baby. They have hardly any hair, and how dirty can their little bodies get? Swish swish, you're done, wrap 'em up.

And poop in the tub isn't the end of the world, so I wouldn't withhold food for that worry.

I wouldn't worry about overheating him when he's sleeping. Keep his head uncovered and his loose blankets to a minimum. If your house is a reasonable temperature at night, a fleece pajama snuggly thing over a diaper and t-shirt should be fine, with 1 blanket over top of him.