Some thoughts: I find it works better for me to only follow bookwyrm accounts with my bookwyrm. I don't check it every day so it's easy to come back to record finishing a book and find my feed swamped by even a single user's microblogging activity. Book-related posts are just slower and fewer (at least amongst the other bookwyrmers I follow).
I follow my bookwyrm with my mastodon account so I can boost some reviews to mutuals with a shared niche interest. That works well enough. Aside from them being busy and not seeing my posts
If I wanted to repost something on Lemmy (anyone interested in the original novels behind great operas? no? no? you philistines ;D ), I'd probably copy/paste what I wrote and link to the bookwyrm. Any discussion could happen on the Lemmy thread. If I wanted to save that discussion, I could add the link to my comments on the book.
That's somewhat more cumbersome than your suggestion but not much. My thought is that I'd rather have the bulk of a robust discussion on my microblogging or threadiverse account than my bookwrym because of that overwhelming my bookwyrm feed aspect. This would be especially true if my bookwyrm got spammed by a robust discussion by someone I follow about a book I haven't read. Easy to not read that thread on Lemmy.
As both platforms develop, it might be possible to create a good interface between them. I don't know enough to evaluate that. Just some thoughts from my experience using both mastodon and bookwyrm with each other.
I get stuck because of physical health reasons. My three things I try to kickstart it again are:
The built in reader on my tablet keeps track of time read. It's set at five minutes, so I try to at least get to that target with the free page turner crap.
Reading fluff for five minutes is easier than taking on something substantial. And if it doesn't happen on that day, that's ok, I can always try again later.
This is what works for me. There will be something which works for you, so try and keep trying until you find it. If something doesn't work for you, that's ok. You'll find one that does.
(Have you tried short stories? Easier to complete than a novel.)