I checked the switch, it was fine, looked into the pump, it was clean, vacuumed every corner, cleaned all the fluff out.
Since the broken wire was unreachable from the outside of the heater, I completely took the element apart, crimped the two ends of wire with a piece of electrical connector, then reassembled the whole dryer..
Now it's heating and drying like a dream, I wonder how long it will last.
The lesson learned is, next time anything trips the fuse I should take the time to take the dryer apart. If I would have found the staple a year ago, the heater wouldn't have needed "surgery"...
I'll keep this thread up to date if anything new happens.
Thank you for all the help!