Not sure if this will help, but try adding more space to your /usr/share/openhab2 mount (and then re-install OH2).
In my system, it takes 56M and it is a new installation:
root@openhab:/usr/share/openhab2# du -h --max-depth=1
56M ./runtime
4.0K ./bin
8.0K ./addons
56M .
Try also the following: set DEBUG=true (or on?) in /etc/default/openhab2 and try to see if the log file gets populated (tail -f /var/log/openhab2/openhab.log)
On the other hand… remember that mounting this folder (/usr/share/openhab2) into ramdisk means that all files in that mount will be deleted upon reboot… and as a result, the start script will fail.
BR,
Dimitris