I think that unfortunately there’s no catch-all solution for backups (I still have old text messages on my FP1 that I haven’t gotten transferred to my FP3+).
Concerning installation, I only know what is in public, too – either use the manual installation instructions (note there’s also a stable 1.5-R build now at /e/ image ROM download) or the Easy Installer once it’s updated as suggested by Manoj.