Hi Vircet, I don’t think you should worry too much about the different machines; you basically had Cyberknife, which is extremely successful with low long term SE’s.
It seems that I myself got more radiation (acc. To your estimates) and I had no Spacer either - we’re either both fine or both screwed😩
But if you rigorously followed the bowel and bladder prep I think we should be OK. All in all I think a gel spacer is a good extra layer of protection for the rectum, but my RO told me that his machine was able to shape the beam around the rectum, since everyday I had a cone-beam Xray as part of the protocol prior to active radiation. It ensured that all the structures matched up with the simulation. Yours used MRI mapping so you had the same thing.
Take it easy and enjoy that cruise you were planning - you deserve it! Best,
Phil