Three important questions, plus another question

So my sinuses wanted me dead earlier today. I mean, all-out pain so much that my teeth hurt. My nose was not stuffed up, but that was because it was EVACUATING ALL MORNING LONG.

I know; you're really glad I started my post like this.

I went to Walgreens and asked the pharmacist what would be best to help -- and that I didn't know whether this was allergies (it came on very very quickly, so that was my guess), or the end of a cold I thought I'd gotten over, and was there something that would work for sinus pain and runny nose regardless of whether it was a cold or allergy?

She suggested Claritin-D / Allegra-D / Whatever-D, and told me that the generic was exactly the same. I bought the generic.

It took two hours to kick in, at which point I was able to take a nap. When I woke up, the symptoms were back (not as bad as this morning, though I can feel them slowly getting worse).

The box says "Do not exceed one dose in 24 hours." Now, with stuff like ibuprofen, I figure I can exceed "recommended dosage" every once in a while if I have a bad headache--my GP says that's fine. But this doesn't have a "recommended dosage," it has ONE DOSE. NOT TO BE EXCEEDED. 24 HOURS.

Three questions:

1) Am I going to DIE if I take another?

2) If I am going to DIE if I take another, can I take something else (like DayQuil) to try to help? (As far as I can find on the box, there's no other sinus/allergy/cold medication that is contraindicated. Only the usual MAOI / high blood pressure meds.)

3) Should I have gotten Claritin-D or Allegra-D, and not the generic?

And the other question:

Did anyone else in Chicago (or around Chicago) have sinus pain/runny nose today, when you didn't have it yesterday? I want to figure out if this is allergies, or if this is more of the cold that I had seemed to have gotten over.

ETA: I can't go out and buy anything (Neti pot, other Vick's, etc). I happen to have DayQuil and NyQuil in the house, which is why I asked. I really hope I can find some way to fix this, otherwise I don't think I'll sleep at all tonight. It hurts too much and the runny nose is... yeah.