Yes, the odor is most likely mold, mildew, etc.

The real issue here is the a/c leak. The best thing to do is add some UV dye to the system then use a black light to look for the leak. If you don't see a leak where the screw contacted the condensor, other common places for a leak would be fittings, compressor shaft seal and evaporator.

If you cannot find UV dye anywhere under the hood, try the expansion valve under the passenger side dash and then look at the condensation water that drains under the car. If there is UV dye in the condensation water, then the problem is a leaking evaporator. That is the worst situation because it is a big job to replace.

Leaking out from April to June indicates a significant leak that will easily be found using the UV dye method.

Best of luck,