Breaker will be available on Ebay etc as below as I doubt original type is still available.
Ammeter the same.
You will need to select appropriate size though.
Forget your voltage readings as they are not the cause of your problems.
Motor problem will have nothing to do with the capacitor as previously mentioned, so just a waste of time and effort replacing that.
More likely either motor bearings are dry or the motor commutator is dirty or the brush material worn out.
The latter could simply be brass feelers rather than...
At that age it could be on the verge of being an electro-mechanical timer.
Either way, disconnect the feed to the timer.
You may need to jumper the "auto" to the oven control.
Deja vu...????
Could swear I've seen this query previously.
Then, as now, the answer is absolutely, otherwise there is no return path for the signal to the mosfet gate.
Signal is floating and will create erratic behaviour at best, nothing at worst.
Generally yes but it is a fairly broad query.
Details of what is existing and the intended replacement would help to clarify.
Current level is also an important requirement as is AC DC.