Exhaust manifold heat shield bolts

I have sprayed sone acetone/atf mix on these bolts a couple times over a few days and tried removing them today when the engine was warm after driving the car. I only have a 1/4" wrench for the bolt size, either 8 or 10mm. None of them felt like they would budge. I have been reading about people trying to remove them, sounds like it's common they break which would be good to avoid. Anyway this is the worst one,



Looks very crusty, just wondering if there is an approach to something like this, maybe hit the rust around the bolt with something? It almost looks like it's been welded on..

Any suggestions would be great.