Coolant sensor and fan

My low coolant light is on still, I just replaced the thermostat and put in new gaskets for a great seal. My 2 problems with this latest endeavor are that the brass knob on the top of the thermo will not move counter clockwise and the slot which I assume is for a flat head screwdriver has been stripped. ANY suggestions so I can make sure the air is totally out of the system? Secondly the coolant sensor is around the battery, is it a removable plug or what? Also my stinkin fan only works on 5 which I can't figure out why this has happened. THANKs to those who helped me out with the thermo replacement and plugs!! Great forum!

The blower motor resistor is the cause of your hi-speed only issue.

The coolant level sensor may be mucked up with sludge. It's easier to get out if you remove the battery. Clean it and reinstall to see if the light stays off.

As far as the bleeder valve near the t-stat, you may be able to get a pair of pliers or vice grips on it to get it loose.