Broken and unbreakable bolts HELP

I removed my exhaust and intake on my slant six today. I broke one of the bolts linking the heat riser to the intake and there is another bolt that was already broke on the heat riser towards the engine block. First question does anyone have suggestions on how to get those broke bolts out? I planned on replacing them anyway but I need to get it out.

Second question I can not get the exhaust manifold and the exhaust pipe separated. I have tried breaking the bolt and loosening it. I can't get it loose because I can't hold the nut and the bolt at the same time. I can't break it for the same reason. Any suggestions on separating them?