In that example, the M301 command should be deleted. The relative order of the M143 and other M commands doesn't matter
If you don't have a resistance vs temperature table for the extruder thermistor, or at least a B value, I suggest you either calibrate it against a thermocouple probe or get a different temperature sensor.
There are separate wiki pages on how to configure thermocouples and PT100 sensors.
The thermistors in Chinese bed heaters typically have a B value of 3950.