sorry to break it to you, but you are fucked.
I had this same thing happen when I ripped apart my rear end (and front end) The bolts would seize inside the bushing, and no amount of penetrating oil (applied daily with impact wrenching for soak in for one week), hammering, or torquing would do a thing. The only thing I accomplished was bending the actual subframe where the arms were mounted...which required a new front subframe. My solution was using a disc grinder to cut as much of the bolts protruding on either side of the subframe off as possible, and then with a high-quality deburring bit on an air grinder, grind away at the bolts unill there was enough space to remove the entire arm. Once I actually accepted that I had to do this, it went fairly quilckly and with minimal damage to the subframe, but the front subframe had to be junked from all the hammering I did.