At a first glance I don’t see anything wrong with your setup or logic. Two comments:
- See how you fare with sync via iCloud; whilst I think it is perfectly reasonable to try it, numerous users here on the forum have complained that iCloud is unreliable. Others, however, have remarked on trouble they have had with other cloud providers, suggesting there is an element of luck or other user-specific factors at play.
- To the best of my knowledge encrypted DT databases are in effect disk images; they can grow in size to the maximum size you set when setting them up. They do not, however, shrink (this is not specific to DT, but a limitation of the way operating systems handle sparse images). I posted steps which I successfully used to reclaim space from an encrypted DT database here in the German language section of the forum. If you do not speak German, and a translation tool such as deepl doesn’t get you there, post back here and I’ll translate the post. Note that at the time the steps worked on macOS 11.3; I’ve not repeated them on 12.x.