Thanks for the confirmation it does handle larger files.
I got the file working but had to wait to test it till now. I still don't know why CR3 didn't like the book. It's came as an epub. It would open it just fine but couldn't remember the last place.
I had to pretty much strip all the pics out which were just a bunch of underlines but kept only the necessary ones but I got the FB2 working!
I use both Fictionbook Designer and Book Designer 5 for FB2 conversations.
Calibre doesn't seem to like FB2 format much, especially with the TOC which is why I have started using FB2 because epubs in CR3 need a inline TOC and then they don't always work.
I also made a new epub and this one works but will use FB2 cause of the TOC works unlike the epub's version.