Thanks for the tips, Paul. I appreciate your quick response and I'll look into aquarium sealant.
I did a bit more research on the cracking issue - turns out it's not related to voltage, but happens with all laser cut acrylic according to people on another forum. The people in this thread found that cracks in laser cut plastic happen even without gluing, and are accelerated by solvents. I included one of the relevant posts below. Does this issue sound familiar to you?