I would discuss my findings with Hensley on the phone. They are very helpful. I'm no metal expert, so I can't comment on the quality of the weld on the screw jack.
I believe I would go ahead and replace that screw jack, and keep the old one as a spare. ~$125 I believe.
The mount doesn't bother me too much, but if I recall correctly they aren't too bad expensive. I'd definitely ask Hensley about it.
As far as the cracked head, you need to get that fixed. There have been a few units that failed at that point. A good welding shop should be able to fix that up just fine. They should also add a few extra gussets for extra support. That part isn't a section that has to be in there perfect, as the spring bar bushing does the work. I'd take the bushing and the head and have them look it all over and add any reinforcement they deem necessary.
I imagine the welding work would be in the $100 range, give or take.
Hopefully they can get to everything without having to disassemble the head, but if not, it is what it is.
As it sits right now, DO NOT USE IT. It appears the previous owners didn't exactly take care of it. The screw jack wear is from lack of lubrication. The crack in the head is likely from allowing the strut bars to get loose. When that happens, bad stuff goes on.
