I have a username and password for the beta forum but they don't work.

I can login to the beta just fine, but for the last few hours my character won't load.

It just sits at the loading character screen for ever.

I have played earlier today just fine.

If you got your beta key from Curse you will not have access to the beta forums.

You are still tied to the NDA, so your options are to use /feedback or /bug in-game or email their support team.

I can't even find the url to the official forum. I didn't get my invite via curse but I have no idea how to do this.

It would be in the email you got that invited you to the beta.

The beta is closed due to "unexpected maintenance" untill 12pm EST, that goes for the forums aswell.
There will/can be minor windows in time where you accidently can log in, but you'll also be logged out frequently.

When I try to login to the beta forum (link provided in invitation mail and I didn't get it from curse), it says I need to reset my password, probably because an admin recently changed my account information (which I know nothing about). After I give them my email the second time for the password reset, it says I've been sent instructions on how to reset my password. That never happens.

And I did double check my mail, tried another unrelated email and everything confirmed it was the correct email address.

Of course I also submitted a support ticket or whatever and - I don't know if this is a joke or something - it says they'll do their best to respond within one business day, which is curious on account of it being a beta weekend and all. Needless to say I got no response.

Are you sure? That would explain why I can logon but can't get ingame (only get to character creation/selection).

Man I wish curse beta testers had some sort of warning somewhere too...

I tried logging into the beta forums about 6-7 hours ago and got the message that it's down due to maintenance.
The other part about sometimes being able to log in is just from previous experiences with other mmo's and their maintenance.
Afaik the character selection is a different part of the server/completely different server, so, while you potentially might be able to look at your character(s) you still can't log in game and actually play.