congratulations on following through to achieve the fix. Maybe start another thread for"apt breaking database"...

This is JFYI: I tried out livarp_0.4.0 based on Wheezy, it doesn't have LightDM, it actually logs in with startx, but there atril works fine. I installed there PCManFM, atril, gvfs stuff which starts automatically and I'm getting my open with last state.
Concerning apt database errors, I don't think it deserves a separate topic. Againg FYI: I found out that it happens on wattOS, Debian Live CD and a small thing called debtailor. It happens when installing on btrfs and runnig kernel 4.x Liquorix series. Didn't test other cases. I doesn't happen on MX, antiX, linuxbbq and livarp. Maybe I didn't test long enough, but for me it looks like these are early failures.