The tube appears to be toast, but have it looked at by someone that does it for a living. 531 steel tubes are easily replaced by competent framebuiders. That would necessitate a re-paint after the tube replacement and frame re-alignment. Probably come out to at least $300-$400 all told.

Practically speaking, you might as well find a good 531 frame and transfer your components over. Unless you're attached to that frame for some reason.....