The bumper fix looks dead simple if it's ONLY the bumper (no fender involvement). Polishing compound (or less) will take the rub marks off. If there's no significant paint damage, the surface work is just a few minutes' worth. As for its alignment, the whole bumper cover unbolts and the supports underneath can be bent at will and then covered back up with the bumper cover. The cover itself is very flexible and can be convinced to line up. It just takes some patience and manual labor.
On the engine maladies, I wouldn't be surprised if it's something as simple as a cam sensor or coil pack either. Your assumption of the aftermarket fuel/timing band-aids is pretty good too. Either way, it likely wouldn't be expensive or difficult to fix.
Are you sure you don't want to pick that up and take it straight to Rogue or TDR for some therapy? Given the troubles it has, you should be able to get a bargain. (You know it's easy to fix, they don't or they would have fixed it).