We need some carnage pictures.
Ohhh...
CARBON steel failures.
It seems like many old steel bikes have a finite wear life. Perhaps exacerbated by overheating or poor brazing (which you won't know until it is too late).
There are quite a few good used bikes and frames out there. You could simply transfer all your old parts to a new frame, or perhaps pick up a bike, and choose the best components between the two, and have a few spares.