I would recommend to do a full backup of the (decrypted) home partition. I had some troubles decrypting the home partition on my linux machine. After that, you have nothing to lose and can play around.
The first starting point would chroot rootfs
There you could ssu re and tell us, to which version the repos are set.
Read a bit more about the topic: Tried to update doesnt boot aynmore - #10 by nephros
And maybe also here: Tried to update doesnt boot aynmore - #44 by Drekkarian
Nevertheless, the content of /var/log/systemboot.log could also be helpful.