I hope this helps.
Make sure you unplug the microwave and stay away from the HV High Voltage section.
Let's discuss the thermal fuses first.
There are four on your model.
1. One is on the magnetron. It will fail if the magnetron gets too hot. Usually because it is failing or the fan is dead. (Both are fairly rare) Or a child inadvertently hit 60 minutes on a potato instead of 6.
2. One is the cavity thermal fuse. Same as above. A child may have inadvertently hit 60 minutes on a potato instead of 6. It is a bit hard to reach physically, but can be tested without disassembly.
3. One is called the hood tco. It actually operates the opposite. It will be open normally and close if the cooktop on the stove below gets too warm. This thermal fuse will turn on the vent fan to cool the microwave. It will reset when temps lower. It appears you tested this one and its ok.
4. One is the bottom thermal fuse that will fail if the cooktop down below gets too hot. Opposite of number 3 above. The hood and bottom tco are behind the controls board and user interface. It also appears you tested this one and it s OK.
1, 2 & 4 above should have continuity. 3 no continuity unless it is hot.
Your measurements of the two thermal fuses behind the control board on the bottom likely mean they are OK.
There are three switches on your model.
NOTE: On switches the term is 'Normally' ... Normally Closed NC or Normally Open NO. "Normal state' means door open. Do test them after you pull the plug off the switches. The circuit can affect the continuity test.
Switch one your primary switch is the bottom one. It is NO or normally open. Meaning door open, no continuity. Door closed, continuity.
Switch two is the monitor switch or the middle one. It is NC or normally closed. Meaning door open, continuity. Door closed, no continuity.
Switch three is the secondary switch or top one. It is NO or normally open. Meaning door open, no continuity. Door closed, continuity.
Your primary switch appears to be the culprit and yes, it blew the fuse via the monitor switch. You said "The primary lower had continuity before pressing button." It should have NO continuity when NOT depressed. It is in line with the HV High Voltage circuit and you will have no heat if it fails to close when the door is shut. You also said it blew the fuse. The monitor switch is the fail safe and will blow the fuse when the other switch is bad.
You'll need to replace the Primary Normally Open, Monitor Normally Closed, and fuse. (It is always recommended that you replace the monitor any time it shorts to blow the fuse.)