BookFusion
Book fusion is a service that allows you to upload eBooks to the cloud via a Calibre plugin. The free version limits you to 101 books with a limit on file size. There is a paid version that is not that expensive right now. I may try this thing out for a while to see if it's worth it.
So it looks like when I synced "all books" and reached my 100 book limit, that was a hard limit on uploads, not on books stored. As far as I can tell from what I've tried, BookFusion will not allow me to upload any more books until I pay for a membership. I don't think I'll be doing that any time soon so I've basically bricked this app, made it unusable.
Will probably uninstall.
Turns out maybe the app just needed some time to restart the limit. I tried uploading a book and it worked, so I'm guessing I can start uploading again. Just need to decide what books to upload.
Might just upload comic books a chunk at a time to read on LGPhone