removing any tool from the kit seems like an exercise in frustration in this particular instance.
I don't have any oder problems w/rust busters. Perhaps it is because I don't run the vehicle while doing the work (but the amount of heat I've applied
after has burned up alot of that stuff - still not too odoriferous 4 me). I have asthma & think I'm pretty sensitive too.
Anyway it seems that 'mechanical' and 'heat' R the only 1s you've left ur self. 'Cherry red" w/a torch (if not simply the regular counterclockwise wrenchin at first) is my usual. I start w/the easiest & proceed up the chain of options as needed. I spray down'n soak over a few days if possible. I start my 'twist' then I may back up (go clockwise a lill) & go back to ccwise (thru out the 1st 1/4 or 1/2). I have a lill 1/4 inch battery impact, 1/2 pneumatic and a big monster. I work my way up if needed attempting to save the stud or bolt. Each case is different. It's tough to feel the difference between a fastener unscrewin frm it longtime home and it twistin in half when snappin off'n breaking. Removing the tool 4 a look periodically can help.
"...break and will have to be drilled and tapped"
this is SOP with about 1/3 of the exh. mani wrk I do...
One thing that increases the difficulty is breakin off a drill bit in the wrk. I just got onea deze in an owner's DIY break caliper wrk. They are hardened metal so create more pain for an already not fun job anyway. :roll:
Creativity, thoughtfulness, ability to slo dwn, partners, alternative tools to try - all help in the automotive shop. Expect the worse, plan 4 it & U might save ur MH & lower ur frustration level (or not).