I'd drill the ends of the crack, if the crack doesn't go to the edge of the sheet, so the crack cant spread. Then I'd hit the crack wi weldon 4 to try to fuse it, then put some more acrylic on top and support the bottom very well, fully. After that I'd hold my breath that there's no leak between the bottom sheet and that front sheet. With that big scrape or whatever I can't tell if the joint at the bottom of the front edge is solid from the pictures.
I know I wanted to but the two overflow holes are in that big box on the one side. only thing I don't like about it is that overflow box on the side.
What you have there is a curved peninsula style tank. The internal overflow with the weir is good in that all the overflow and return plumbing is hidden. That's also probably why there's no background?
How many holes are there in the box?