Even if the resistors pack was blown/out, high would still work cause it by passes the resistor pack.
I have never tested a relay by reading its resistance. Rather, I put power to the control circuit and see it the load side opens or closes the circuit. Sometimes it is possible to switch the relay with another to see if there is any change. Before taking blower motor out, I would check to see if there is power going to the blower motor and check also for ground. Have seen sometimes the connector pins aren't making good contact. If the blower motor is getting the power and ground it needs then blower motor needs replacing. If it is not getting powers and grounds then wiring to blower needs to be checked