Q: I'm having a horrible lack of power issue

It started out with being slower and slower to start and then some hesitation, then all of a sudden when I was driving up a hill it started backfiring out of the intake and maxing out at 3000 rpm, if I hit the gas slowly it runs rough but tops out at normal rpm but if I hit it normal it maxes at 3000, now it doesn't even have enough power to get onto ramps. Since this happened I've replaced the distributor cap, rotor, pickup coil, crank sensor, and the timing chain, none of which helped at all, it has been throwing different codes some to do with the crank sensor, some with a lean condition, some to do with the o2 sensor circuit, I'm not sure if it's related but when filling the fuel tank all the way up it leaks a big puddle once I am done but it doesn't leak after. I've tried everything I can think of and nothing is working so that's why I am reaching out to see if someone else can figure it out

My car has 160000 miles.
My car has a manual transmission.