Hi kdcisit — Regarding your second question, the default setup for the web UI loads assets (such as javascript files) from a cloud server at ui.opensprinkler.com. You can move those to your local OSPI and serve them up from your nginx server, which would solve your mixed-source SSL/TLS warning.
For info about how to do this, check out https://openthings.freshdesk.com/support/solutions/articles/5000164006-using-a-different-server-for-ui-assets
Hope that helps. Cheers