radiator fan doesn't come 'but works when to wired io battery

You have more than one issue. The blinking check engine light is caused by the misfire, that is what P0300 is all about. So you need to fix the cause of the misfires. I think that the other code may be misprinted because a P1807 code means that the 4-wheel high indicator is shorted to ground. I don't believe that you mentioned that your car was 4WD? The cooling fan is a serious issue. There are relays, sensors and the main computer that needs to be properly diagnosed, or you might severely over heat your engine and ruin it. here are some shops: https://repairpal.com/pontiac-repair-in-princeton-texas