Edit: on my phone I missed the part where you had a jack on it. There is no secret to the adjustment. Loosen the nut, the bolt is supposed to turn. Buy good blades for the Sawzall.

Note that caster change affects camber in the same direction and vice versa. The FSM lists approximate amounts but it means that adding more camber will also add caster to your current settings.

My 84 & 85SD had 1 bolt each that was locked up and couldn't be removed easily as per the FSM. I ended up cutting them with a Sawzall. I was refubishing my suspension and had the spring removed.

For adjustments, I would use a cheater bar and force the issue. You can try spraying but it will be difficult to get into the area that is rusted. You have nothing to lose if it is out of adjustment. Your suspension also probably needs attention if it has been installed long enough to be that rusty.

I wouldn't hire a professional because they don't fix everything without running up a huge bill.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.