Should the rubber centre of the rear engine mount/roll stopper on a TF Magna (3.0L) touch the top of the metal ring casing? Mine seems to have a 0.5cm gap between the black rubber and the top of the metal ring casing?

It's stuffed then. Replace it and also check that the subsequent stress hasn't cracked the front mount or the side ones too.

Cheers. Might also explain why the engine moves a bit when in drive/reverse with the brakes on. Looks like a bugger to replace though.