First of all, never use a slow blow fuse unless it's called for. You risk burning up a component or the wiring harness and then stuff starts getting real expensive. Second, do you have air conditioning or not? I have air and don't have a "ceramic resistor block" next to the fuse block and my wiring diag. doesn't show one for either application. Can you attach a picture so I can see what we're dealing with? If I was going to hazard a guess, I would say either your blower motor is going/gone bad, has something stuck in the squirrel cage keeping it from turning freely or the wire coming out of the back of the fuse block has burned through. I would probably start by disconnecting the battery and taking the fuse block away from the firewall and checking the wires and connections in the back. I would also take a hard look at the resistor block and see if it looks factory or if someone spliced it in for some reason and if it is indeed in the heater circuit. I hope you have a volt meter and can measure continuity. You'll need it. If everything looks good here, measure the motor itself and then get back to me. Worst case, you can always load it on a trailer and bring it down here and I'll try and track it down for you.
Steve