What's wrong with this picture Part 2, but much more serious this time.

First, determine if that is just stress cracks, or in combination of internal rust-induced stress cracks...
If the metal is solid, weld it up; and then fish plate all the sides you can get to. And don't be shy about it.
Don't mess around with a 110 welder on that, either. If you don't have 220 in your shop yet, rent a generator for the day.