Yes you can reach the direct UI by setting webserver to ‘Standard’ and under 'Network", show disabled ports, and put a port (ex 7777) there. After this you can go to http://yourha:7777 in your browser and you should see the DSMR Reader UI. But be aware that this disables Ingress support.
Regarding the backup question, all the data is in the DB you are using. So if you want backups of your data, either backup the database or use the Dropbox backup options.
Not sure if you can remove the homeassistant db. For specific questions arround TimescaleDB you can ask them here: https://community.home-assistant.io/t/home-assistant-add-on-postgresql-timescaledb/