I’m indeed sorry that I can’t tell you something better.
I mean you need local, professional assistance.
Is there any company near you which does car engine repairs?
If M12 x 1,5 mm is correct (what I hope) then we had the same thread as that on oil drain plugs of cars (Helicoil inserts in that size are available without problem).
Also, you need their experience - they should be able to tell you whether the screw/disc securing method would work in combination with Helicoil, respectively they can recommend an alternative method.
(I personally would think that works, but really don’t know.)
Furthermore, I’m sure that such a company also has a M12 x 1,5 mm fine pitch drill - to repair oil pans. Perhaps they can refurbish your frame threads.
Keywords;
Cylinder grinding shop
Turning and milling
But I’d expect here also massive trouble, you can’t buy such “high performance” adhesives at the local DIY market or Amazon, the “really good stuff” will be reserved for experienced companies - industrial use.
So, you end up in the same situation as above - you need professional help.
Well, however…at your images, the thread doesn’t look so bad.
Maybe it is possible to recut it.
Did you ever repair threads by yourself?
