Skippy, have you got a close up photo of the Staining ?
If the Chemicals you have tried have had little effect, I would start doing test spots starting with a light Polish/Pad Combo gradually moving up to a heavy Compound and even Wet Sanding if required. Sometimes there just isn’t enough Paint to remove the defects and repainting is the only option.
It would probably be easier and cheaper for you to get a GOOD local Detailer to have a look at it for you ( I may know someone in your area )
For protection you can’t go past a good quality Professionally applied Ceramic Coating although there are consumer grade coatings available prep is key to a good result.
Jason