The snake is XLR. The cable we ran from the board to the amp was a 1/4 speaker cable. And I'm not sure what output we were using. As I'm not with the board right now. However I did find that the main problem that we have is the fact that we had the board set on MONO BRIDGE. And that is not correct for our application. It should be set at AUX1 MONO or AUX 1 AUX2.
If you've got a couple of stage monitors, then yes I would set the board to Aux 1/Aux 2, set the power output to the output that matches the rating of your monitors (100W, 300W or 500W) and connect the monitors to the board using speaker cables connected to the speaker outputs on the back of the board.
You can then connect your Peavey power amp to the "ST OUT +4db" jacks on the board, via 2 of the return channels on the snake (you will need a couple of TRS Jack to XLR male adapters if your snake returns are XLR sockets).
Once you have done this it should look similar to the diagram I've attached. You should now be in a good position to start troubleshoot the microphone gain/limiter issue.
Many apologies if you've already got further than this, but troubleshooting without being able to see what you have/haven't done takes a bit of time.
Best regards, Simon