If you go with stallion 1, then according to your figures that would put her at a minimum of just about 9 and 1/2 months if you use the 282 days figure. That would mean appox. 6 more weeks left. I honestly don't think you have 6 weeks as she was clearly developing a bag through out the previous month. She is also showing signs that she would be closer than that if I look at everything you are posting about. The tail rubbing, the laying down alot, increase in the amount of stools and the softness of them, the shift in the position of the foal, and the appearance of her rear muscle tone relaxing. I could be wrong, and as I have said before that seeing in person is a bigger indication. But if she were mine, I certainly wouldn't let down my watching at this point as she could go any day. Again, just my opinion from what you are describing.
Still, she is most definately much further along than than what she would show with stallion number 2. There is NO way that she would look this pregnant with stallion number 2 and according to your number of 179, that puts her just shy of 6 months and your vet said that she was at least 6 months. No, my mares start to get wide at this point, but typically I can't see the uneven balance of where the foal is laying at 6 months. In my mind I would definately rule out stallion number 2 just on your vet statement alone.