1. I imagine you're doing something like trying to access it via some form of DNS bounce (e.g. http://router.yourdomain.com, with "yourdomain.com" being handled by dyndns or equivalent). Or you did something like only allowing the router to listen on its WAN IP address. Cant really say without seeing the config though (I mean, it's all guesswork). Try accessing the router from whatever (LAN) IP address you assigned it (i.e. without using DNS / a hostname). If that works, yay. If that doesn't work, yep, ssh may be the only way in.
2. The correct course of action is to set the router up to listen to the LAN side (if it's not), and then set your DNS server to point "router.yourdomain.com" to its LAN IP address, rather than the WAN IP address.
3. Port forwarding would mean that the port gets sent to whatever device on the LAN - it would actually prevent you from communicating with the router on the forwarded port(s). Assuming you didn't delete them, you shouldn't have to recreate the forward rules.