Use the propane tank from a gas grill to bench test your Dometic after doing
all that work, and before you reinstall it. The gas regulator on the gas
grill is set the same as the Dometic. Threads on the hose match right up.

 The millivolts that the thermacouple produces,probably isnt holding the
magnet.Bus boys sells them , but for the price they charge , you better hope
that is not your problem.Dont throw parts at this. If you get the dometic
started on high, turn the thermistat to low and let the couple cool down.See
if the gas vlave snaps shut then.

While you do have the Dometic out, slide a  piece of heat shrink tubing over
the electrical ignitor cord and to where it meets with the box. The will
prevent misfires when striking the start button. All you can do is lubricate
that plunger shaft to ease it up.