I have a sump 30 gal long with a similar problem but not exactly like yours, I cracked it fiddling around with the connection (my bad) it has one crack similar to your small crack on the side not bottom.
I took two pieces of 1/4" plexi and siliconed the heck out of them, sandwiched the glass and used the bulkhead to secure both pieces of plexi.
It's been that way for 3 months no problem, I will replace it soon, but your load is on the bottom and that crack is much bigger. I would look to replace it.