Hi all, just to report back about how I resolved this.
It was indeed the XFS filesystem that got corrupted badly. Repairing that required installing XFSprogs which I couldn’t do because using apt-get to install gave same errors.
I’ve come to understand that installing plugins and rebuilding the app is a memory intensive task. However, I have a small forum with dito hardware underneath 2GB ram and 15 gb disk space. Had no swap enabled and my hypothesis is that I ran into memory issues because I had to reboot the system a couple of times while trying to install the plugins. Probably not good for the filesystem and XFS put safeguards around amongst others the GIT folder.
So I pulled a backup (fortunately on S3 so no issues with that), made backup of the app.yml file and respawned the VPS and setup SWAP with this guide (debian VPS). Under an hour I had things up and running again. Few 
And the reactions plugin I set out for, working great!