There are two ventilation slots at the back of the viv lid, I have them open about half way at the moment, which probably equals and inch on either corner. I can open them more though but it concerns me that any crickets in there will escape...lol.

Water features - we just have a water bowl on the floor. Havent got around to putting anything else in yet as not sure what to do.

Havent a clue what a Pothos plant is, not sure if we get it in the UK. Also what are snake plants?

Nah Ive relaxed about the humidity, so thats not a worry now.