It wouldn't surprise me if the rubber hose has worn through on the top of the differential housing and is the source of your leak, plus as mentioned by
@junkyardhero that fuel pressure regulator is in a terrible place. Whoever did this disaster needs a kick in the head with a steel toed boot, that is nothing more than a slow fuse to a devastating fire. It must be corrected asap. Looks like a good part of your lack of power is solved, keep at it, even if you don't keep the car, the experience and knowledge will serve you well when you decide to buy another one.