If you're burning through multiple resistors (as in they actually test bad), you can be pretty sure it's the blower motor.
If you're melting the harness or connector, you can be really sure it's the blower motor.
When you've done both, just replace the blower motor (and any damaged components), because it ain't gonna be anything else. Motor goes bad in the right way, it eats resistors, melts wiring and connectors, and you end up where you are right now.
2006 WK Laredo 4x4 4.7L
1993 ZJ Laredo 4x4 4.0L — Dead, sold, and rolling again