New Pacman, questions!

[4mb3r]

I just got my baby pacman. He is probably about the size of a half dollar maybe? I just have some questions..
What size habitat should it be in? I have it in a 6qt(shoebox sized) sterilite container with moss on one side(was given to me this way) and theres a bowl in there for water.
What is the best substraight to use?
How old/what size do they gotta be before there sexable?

I am completely new to these guys so any information would be helpful!! Please feel free to mention everything I didnt ask as well. Just wanna make sure im doing the best I can for him!!