A 5 amp fuse will
work, it would likely blow as soon as the motor starts and definitely would blow when the heater came on. Also the thermal fuse is there to protect against a thermal event. The thermal fuse is rated to open around 208 degrees. Loose connections on the thermal fuse can cause high resistance which will create hot terminal connections which can cause the thermal fuse to open also. The dishwasher will pull between 8-10 amps when the wash motor and heater is on.
You will need to install a new thermal fuse kit part #675813. Follow the instructions that will come with the thermal fuse kit and use the new wire leads that will come with the kit. I added the wiring diagram in the image below.