I don't see any major problems. I just think you need to put the grate guard on the main drain, so any leaves or snails won't be able to get in there and clog things up. Personally, the pipe for my emergency drain doesn't go beneath the water line in the sump because I want to heard if any water goes down that pipe and alert me to check on it.
You do want to make sure your sump is big enough to hold any water draining if your return pump cuts off or dies.
Other than that, the only way the water level can get too high is if your pump is variable, but you said it is not. Might be good idea to double check the return pump and take it apart to clean, check the impellers and magnets.
I would check the overflow level over the next couple weeks, and see if it is slowly creeping up. If it is, then it's just a matter of opening up the valve a bit more to accommodate it.