Code P0302, engine miss?

No, not unless you're replacing a component, so for example, if you replaced the compressor, you would drain all the oil out of the old compressor, measure that amount, and add exactly the same amount you took out. The oil doesn't leak out like freon. It stays in the lower sections of components because it's not in a gas state like refrigerant is at some points. So don't worry about it. Just add some refrigerant. Keep an eye on that pressure vs temperature chart I posted up top. Since you're not adding per weight in this case. You'll be good. I just prefer tp vacuum the system down because it removes air and any moisture.

Is there oil leaking out of the system anywhere?