Dome Nut and Stud Issue
 

I'm working on a 1976 2.7 and found the lower of the two dome nuts behind the engine oil cooler was loose. explains one of the oil leaks.
looked in the bentley manual and it says 25 ft lbs
torqued it down and i felt a pop. tried again and would tighten but not to torque spec
so, i'm thinking it is stripped on the inside and the stud is pulling out. i put two nuts on it and turned it back in as far as it would go but now i'm hesitant to put 25 lbs to it. i did tighten it pretty tight by hand with a ratchet but i'm afraid once the motor heats up it will pull out again and i'll be right back where i started.
any suggestions as to how to remedy this, if there is a remedy?
i thought about taking the stud out and putting some red locktite on it and putting it back in. maybe jb weld? i'm stumped here. i'd really like to avoid splitting an otherwise perfectly good case

question number two: the o-ring behind the washer. can i use any o-ring that fits or is it a special o-ring? i used a thin red one i had which looks correct (considering the squashed one that i took out was also red) but may be too thin. i also have some green ones that look like they'll fit just as well. but i'm not sure if the heat or stress requires a special ring

as usual, thanks for any suggestions

The inside case is a standard thread, 10mm. I don't think loctite will hold bad threads, so it's JB. there is usually 2 extra o rings in a bottom end seal kit for the through bolts. Use either green or blue has been in the bottom gaskets seals.
Bruce