Caliper Carrier Bolt removal

[Mr_Owl]

Yes, the dreaded aluminium vs steel corrosion has got one of my carrier bolts almost solid. With a breaker bar and a bit of scaffold tube, I can turn it. Just. The top one came out no bother, the bottom one is binding. Have applied PB Blaster over a few days with no change.
The D3 is my first experience with aluminium parts so I don't want to bugger it up.
My next move is going to be boiling water treatment. I can get a blowtorch on the bolt, MAPP gas on a Rothenburger torch, but is this going to cause more harm?

I could just leave it, as I can get the disc off as it is. But that doesn't sit right in my head and I plan to keep the car for a long time.

I am also wondering what state the pinch bolts are in and if I should be doing some PM on them...
Thanks