That bolt looks to be broken off above the lower unit so its likely is not holding on to the lower.
Wooden wedges are your best bet at this point.
Gat after it.
Agreed get the tab out of the way.
Not sure what you have for tools but a few things to try on the cheap would be to use a dremel and carbide cutter to grind in some new flats, cut a slot and try a hand held impact driver, hammer on an old socket or drill just the head off and leave the stud to...
Do you or a friend have a welder? You could weld another nut on the rounded off head and give that a try. The heat that’s applied helps as well. As for the other broken bolt you would be surprised how much holding power that has even without the head on it.
The weather has down right amazing around here. I won’t even see the 30’s until next week then the 20’a roll in soon after that. It’s been 25 years since I’ve seen the harbors freeze up.
To me the first step would be to determine the cause of no compression and the cause of the failure. A complete tear down would be my first step starting with the head on the failed cylinder to be sure it’s not just a gasket but with zero compression you may not be that lucky.
If that...
Agreed with above. IR guns are dirt cheap and give you a good pice of mind. I have a $60 Kline and $8 harbor freight IR gun and they both read the same.
I do love a hood smoked cheese.
When I was in China I ate a lot of stuff that I had no clue what it was. There was one thing that was just amazing and it turned out to be smoked tofu.