If you let the rye mature and seed out then it will tend to come back the following year. The rye would have to be mowed before it has a chance to seed out to controll it from coming back. As for the weedes in your clover, there are a few sprays that can controll the weeds and not damage the clover and I believe one is post which you mentioned. Maybe some of the other guys will help you out, many of them are more familiar with these chemicals than I am. I have been working on a wick applicator to use in my food plots maybe lawnfarmer can give you some help with that as he has a wick project that should be about complete. Good thing about a wick applicator is you can use roundup to control the weeds and not affect your desired plants. Only drawbacks you might run into is you need level ground while using a wick and the target weeds must be higher than your desired planting so as not to damage your clover.