the gas gauge and the temp gauge both are on different circuits but go through the data stream to the instrument cluster. You can verify the temp sender with a scanner. if the scanner shows the correct temperature then the cluster may be at fault
the code P0446 is for an evap
vent system restricted or blocked. Usually the evap
vent solenoid stopped working. Normally to check this would be to use a smoke machine at the evap port or with a gas tank adapter. with the key off the vent solenoid should be open and with the smoke machine on smoke should be coming out of the canister vent. If no smoke is visibly coming out of the vent then, using the scanner, you would turn the vent valve open and closed to see if it is clicking and it is opening and closing.