Actually, PM me and I can set you up on a subdomain with QuickBox DNS. Then you can follow that guide and have Let's Encrypt covering your server to avoid the self-signed cert nags. Technically, your server is as safe as it would be with an authorized certificate, however, browsers nag you about it since it is not signed by a verified authority, i.e; Comodo etc.
Just let me though and we'll help you save the cost and give you a
<you>.quickbox.io spot. Better yet, it's free