Car runs bad

Your fuel pressure should be 55-62 psi. 65 isn't a problem. But 90 means your fuel pressure regulator is bad. But it won't stop the engine from starting. If the diaphragm is leaking fuel into the intake manifold, that will give you a rough idle and the P0300 misfire code. However, if the FPR is also leaking the fuel back to the tank after shut down, then that will give you a hard start.

Pull the rubber hose off the FPR and check/smell/feel for gas. If there's any at all, replace the FPR. Also, when you do a pressure check, keep pressure gauge connected and turn key off and watch gauge for at least 15 minutes. If pressure falls, replace FPR.

One last piece of advice: Don't replace components without testing them first.