You can develop for any platform, including mac. It will not affect your ratings.

Ratings for your game aren't related to how many games you rate. But if you leave feedback on other games, they are more likely to play and rate your game :)

I'd suggest checking out Wine or VirtualBox, they might help running Windows games on OSX to give feedback and increase the odds your own entry might get more visibility as a result.

Wine is a compatibility layer which in theory lets you run Windows application on Unix systems like OSX, Virtual Box is a full fledged virtual machine so you'd run Windows in a window within OSX. Not sure how either would perform with games tho.

Finally, usually some people submit web embedded games you can play regardless of the OS, so maybe you can just give feedback on those, and any OSX native game if there will be any.