It's fine to leave the fuel pump later, but definitely worth changing the spark plug. As for if it's a stuffed rear engine mount, the only real way to tell, is to jack the car up and stick your head under to check. (visual check is enough to tell if it's stuffed or not) as you have researched, the notchy gear change can be due to that few reason, so I would in the following order to find the solution 1) check rear mount 2) change gearbox oil 3) adjust the shift link point. If all these don't work, maybe check out others MPS3 and see if it's the same.....? (coz it might just be the way it comes with)
Hope this helps.
Oh, have no problem with the forum on tablet.
When in doubt, power out....of control.