Well, this sucks, not only is there no adjustment (your alignment guy did everything he could and was correct) but it looks like your upper control arm is actually even hitting the frame on the rear! That is where we wanted to go in to increase the caster and decrease the camber, bummer. Ok, the only thing you can do at this point without major surgery is to bring the lower control arm forward with the strut/locator bar. That bracket is welded in too, so getting an adjustable one, or making that one adjustable is all you can do.
Now, let's get back to the specs you have to put things in perspective, it's not good having negative caster, you need caster for high speed stability. To give you an example a S-10 pickup has something like 2 + degrees caster while a BMW 7 series has 4.5 + degrees and a bonneville 200 mph car will have as much as 18 + degrees. Having negative caster is going to do some funky things with handling making the tires bit pretty hard with a little turn of the wheel. I would think you need to do something about this and correct it.
Like I said before I am also concerned that the crossmember was welded in wrong and now if you move the lower control arm forward to get that caster needed you are going to be binding up that lower bushing. So take a good look at it and see if by chance the lower control arm is actually back to far at the spindle and maybe moving it forward will make it "happy", you can only hope. Because if it's where it should be in relation to the crossmember, pushing it far enough forward to make up for a misplaced upper control arm shaft may bind that bushing and cause you problems.
And by the way, that strut/locator bar mount looks a little funky, is that rust I see right at the weld to the frame? That could mean it isn't welded well and water got into the joint.