Which ESC Motor Combo?

[Pocket Rocket]

Help Please

Running a Losi Mini 8ight and really going well, but I have an issue where the back end of the motor keeps poping out which then strips the spur gear .

Looking to buy a good ESC Motor combo and looking for recommendations.

I do have an hobbywing 35amp esc spare, should I just buy a motor to go with it?

When buying motors or ESC's how do you work out which motor for which ESC.

Finnaly is the a remedy for the motor mounting plate moving in the event of a bang or bump?

Loads of questions and any help would be appreciated

Thanks in advance