File Access over https safe

I have a mac mini server at home that has a USB 3.0 storage device attached where I store all my files. Anything from iTunes, iPhoto, documents, etc. I want to know how safe it is by creating a VPN connection from my MacBook from anywhere in the world and accessing https://webdav.myserver.com and writing/reading files? Is there anything I can do to make reading/writing more secure? https://webdav.myserver.com will not be accessible over the web unless there's a VPN connection.