Interesting delema there. The angle of the dangle there is such that getting a drill in there to drill it out could be kind of problematic. Not entirely impossible but a real pain in the ass for sure. If it is seized for sure then drilling it out is probably your only real option at this point. Once drilled out see if you can get a pair of channel locks up in there with a small nut on the face of the pin and then squeeze it and see if you can get the pin to drift one way or the other. I have never had the set screw seize up on me and have to be drilled out but I have had a few of those pins that required some work to get out. There is precious little room up there where you are working so the pliers used to press out the pin is the only thing that I have found that works well, make sure that you use plenty of your favorite lube on it and once the pin is broken free push it back and forth from either side until it gets enough lube in and around it to allow it to slide right out.

Mark