This is why I never touch exhaust manifold bolts anymore. I feel for ya, brother!

But anyway: once I was successful grinding two flats on a stuck bolt and using a wrench on it. They say heating with a torch helps, but I've never had a on-vehicle situation where that seemed safe. Back in my starving student days I broke an easy out in a rusty bolt, discovered I was doomed, and so I simply JB welded the bolt head back in place on thhe manifold and drove the car for a year that way. O wait, that was my roomies crappy Nova...

In your case I'd get the manifold off to see what you have. If there is something to grab onto you need three tools; PB blaster, a hammer, and patience. Bathe it liberally with PB blaster and let it sit for as long as you can. Once in a while tap it lightly with a heavy hammer to help break the grip of the rust and help the PB blaster creep in there. Then either visegrips or the flats-n-wrench idea. If nothing to grab onto it's drill and easy out time, which will pretty much require removing the head, after which I'd save the cost of the easy out set and take it to a machinist and use my debit card tool.

And don't stress, just walk away and have a cold one. It'll be ok.