I have 2 problems, the second more pressing than the first, though both are important to upgrading any Leap version. I'll just give a rundown on the events so far.

Of note: my /home is on a separate XFS partition of the same drive, and I ran updates and rebooted before attempting the upgrade.

I tried upgrading Leap from 15.1 to 15.2 via USB since all I have is Wifi atm (so ctrl+alt+f2 -> root login -> init 3 -> zypper dup --download-in-advance is a fail due to losing Wifi in runlevel 3). So I disabled other repos in advance and upgraded Opensuse repos to 15.2.
During the install, it reached approximately 85 - 90% completion, and then started throwing read-only errors during the attempt to install xorg-x11-xvnc, and all packages afterwards. So at this point the upgrade was hosed.
I force-rebooted and selected to boot from the snapper snapshot I made prior to the upgrade. Great - it booted... except su snapper rollback resulted in an error to the effect of, "Couldn't create snapshot ((error 30) - read-only filesystem)". So snapper couldn't make a backup copy of the current ro filesystem and, consequently, couldn't set the current ro image to rw. Soo... I tried booting from the installation USB in recovery mode and mounting the partition as rw so I could check the /etc/fstab, but recieved "wrong fs type, bad option, bad superblock on /dev/sda2". Looking it up, a Suse document recommended btrfs rescue zero-log, which succeeded only in destroying it further; so much so that the ro snapshots would not even mount.

I have reinstalled from the ground-up, preserving my home partition, in the following manner:

-During partitioning, I selected Advanced partitioning and selected:
1. Reformat the btrfs system partition, set mount to /, enabled snapshots.
2. Reformat the swap partition, mount as swap
3. Do Not format home partition, mount as /home

At user creation, I selected to import a user and selected my username that appeared below.

Installed, reboot, and... my home folder appears to be completely reset; everything - but the stock folders - is gone, and all of my wallpapers in /home/(myname)/.local/share/wallpapers are also missing.

So my questions are, most to least pressing:
1. What happened to my user home folder?
2. Can I get my files back?
3. How to avoid this again (still preserving my home folder, but would like to not have to muck with fstab mounting after install, if possible)
4. What could have caused the fs to suddenly go r/o during upgrade? (Afraid to upgrade at all in the future.)