I'd say you're too late. Sometimes I've even been too late with orders placed in the last week or so of the month (eg. the 25th). Just put in your order, and you'll get it when you get it. Think of it as a nice bonus, not a paycheck, and don't rely on it arriving at any specific time.
Also, if you cancel your order later and submit a new one, only the date of the new order will matter.
2) PM one of the admins (look at your previous orders to see who filled it) and ask.
Seriously, though, you need to chill out about this whole thing. Author rewards are a *bonus*, not your paycheck. You'll get it when you get it. If you're in such dire straits that you're depending on your addon author rewards to put food on your table, you should probably stop playing WoW and use that time to find yourself a job you can actually live on instead, or quit blowing all your real money on strippers and coke.
The vBulletin login system hasn't worked in years, since everything became unified under the Curse banner. I have no idea why the Curse admins are too lazy to do something as simple as redirect the vBulletin login URL to the Curse login URL on the server side, but it's been that way for years. Just make sure you use the login link in the top right corner of the site before you try to do anything on the forums.
Better yet, whitelist Curse and WowAce from your browser's "delete all the cookies on exit" feature, so you'll just stay logged in all the time.
There is a cutoff. With 2-3 average daily points it's possible you've dropped below the threshold. No way to know for sure unless an admin wants to tell you, but as I'm still getting points I'd guess that's the most likely scenario.
No, if there's a cut off it's much lower than that. I've been lazy about updating SharedMedia-Blizzard (my only addon hosted here), and I've been under 1 point/day for a while. I'm still getting my .44 points/day. Most recently was 19 hours ago.
I think you need an install base of 1000 users for an addon to generate points, or was it you as an author need that over all your projects to get points. I don't remember. There was some kind of limit anyway.