1. It's not something I've ever tried. I can't really see what advantage it would be. If the WAN is up and you have convectivity to to other end then why switch to a different tunnel? If your first tunnel goes down, for whatever reason, then why switch to a second tunnel rather than bring the first tunnel back up? If you have both tunnels up simultaneously then you could run some failover/redundancy between them. However it's likely both tunnels will be using the same route such that if one goes down both will. You may get a better answer to this in the vpn subforum. ;)
2. Not sure quite what you're asking here. Do you mean remotely access the webgui on a pfSense box?
If so you can do that already. The server that provides the webgui listens on all interfaces you just need to add firewall rules to allow it. It isn't recommended though to have the webgui accessible from the internet.
Steve