Yeah, this is a warmer bag than Golite's 20 degree bag. I've had it down in the teens, using a hooded parka, and was toasty warm.
As to how much down...I'll have to look and see if I can find my records. I lost a hard drive a few years ago, so I'm hoping I still have the printed spreadsheet I used when stuffing the bag. The baffles are slightly overstuffed (think Western Mountaineering) to prevent down shifting. Also, I used a differential cut, meaning the liner fabric is not as wide as the outer fabric. This helps prevent down compression. When the bag is snug against you (which you want to reduce drafts and convection), the looser outer fabric won't compress the down. Whoever gets this bag is getting a very top end product.