I do a lot of acrylic fabrication. For your application, you can use 1/4" since it won't be full of water. The heat won't be an issue either. The forming temp of acrylic is over 350F.
For the assembly, unless you have perfectly prepared edges, use weld-on #16 to glue the pieces together. If you have prefectly fitting joints, use Weld-on #4 or #3 (fast setting). For hinges, you can use the acrylic hinges and just glue them on. That is what I use on all of my vivariums and have yet to have any problems with them.
If you have any more questions, feel free to ask me. I have been doing this for a while and have probably run into every problem you can think of.