That sensor (BANK 1 SENSOR 2)is the catalyst monitor, not the primary O2 sensor, it will not cause performance concerns. You have a code for the heater circuit, as well as a faulty sensor. If you are lucky it will be a straight sensor swap. Ohm the heater circuit in the sensor, verify voltage at the harness connector with the key on. Sometimes road damage will kill the sensor or tear up a harness. Some O2 heater circuits have individual fuses that burn when a short occurs. Simple stuff first before you slam a new sensor on it.
You have a P0300, as well as a P0302. This means there was a general missfire spread across multiple cylinders. Cyl #2 happened to code first. Look for a problem that is common to all of the cylinders, don't concentrate on #2 exclusively. See below.
Agree with Axe Man as well. A bad diverter valve or dump valve will puke fresh air into the exhaust system at the wrong time/place and screw up the O2 readings enough to cause an intermittent missfire. Many systems use the primary O2 sensors as the monitor to verify the AIR system is operating properly. The PCM looks for the increased O2 in the exh when the AIR system is commanded "on". If the O2 sensor voltage changes, the system is working, no O2 voltage change, the AIR pump/valves are suspect. If the AIR system is injecting air when it isn't supposed to, you will often get lean codes as well.
If the secondary air aystem is totally inop, then I don't see how it would cause a missfire code. The only times I have seen them cause missfire codes was due to bad diverter/dump valves.
The newer electric air pumps don't usually have a dump valve to worry with.
