Here's my advice: Take out your rocks and drain as much water as you can out. Clean up the inside of the tank really well. Fill it back up and do a LARGE pwc
to get rid of anything bad you cleaned up and to get the gunk outta the sand. Fill again and start over.
You probably won't have much of a cycle since you're putting back the LR
that cycled already.
This time out I would suggest adding your cuc and any inverts first. Then onto small and not real expensive fish. try some clowns, blennies or a goby. after your tank is doing good for a few months add in the fish of your choice.
I hope this helps and if you need any more encouragement just post!