ambient temps of 90* will not harm the snake unless it is constantly that temperature. So a few days of that won't hurt.

Tap water is just fine to use. No need for distilled or bottled.

I would ditch the repticarpet. When a bp pees they soak the whole bottom of the enclosure. Reusable substrates don't work well for this reason. It will be near impossible to get the smell out.