HELP!!! Subframe Removal 99 alero 3.4L

I am removing/loosening the subframe to get of my oil pan off of a 1999 alero 3.4L. I need to loosen the passenger side part of the subframe to get the oil pan out, but I am having some trouble with one bolt. It is connecting the control arm and the subframe together. It's vertical. Its on the driver's side. The passenger side came off really easy and I have a impact wrench but its still not moving at all. I have tried PB blaster, removing as much tension on the bolt as possible, and I dont want to use heat because if you heat up metal and when it cools it shrinks and that would mess up my subframe. I have hammered away at it with my impact but i dont want to damage the bolt or my impact. So any advice or suggestions would be greatly appreciated.

Thanks,

Jimmy