if the subframe is aligned correctly and there's not too much corrosion, the bolts should go in without any effort.
I can raise the subframe a little more up to the point where the posts push onto the body and raise the car off the axle stands. The rear does not reach the body when the posts do and there is about an inch gap. That might be roughly the length of thread on the rear bolts. I suppose if the front posts were wound tighter that might also raise the rear toward the body? Is there any risk of damage to the threads by raising the subframe further, given that the installed bolts are currently wound in by hand?Can you use the jack to lift the subframe any higher? If you can get the subframe to sit against the body of the car, that'll be the best approach, but that being said, the subframe is not too heavy, using the bolt to lift it up is relatively safe, just make sure to only tighten a few turns at a time per bolt then move to the opposite side, like installing the wheel. Using a ratchet socket or a wrench is fine, just be mindful about how much force you are using.