Honestly, I think you might be overthinking this.
1. Some babies just dont like water ds1 screamed the entire first year during bath time. Now we have to drag him out. Dd loved baths but now ds2 hates them. Like rcw said...it is a few minutes...and if he poops you clean it up.
2. Unless he is sweating excessively, dont worry. Ds2 and dd are both hot kids. I still swaddle(d) them and put them in sleepers under.