Hi Joe,
I own a Dell XPS 15 9530, and it has been having this issue since day 1. I tried everything... Including replacing the wifi card with a new one Dell provided, re-installing the system multiple times, different networks, different cities... I am quite certain it's the card. Here's my answers, as much as I can.
1. 2.4 GHz.
2. Win 8.1.
3. Everywhere. Yes.
4. About 2~5 depending on test site.
5. It's most obvious during gaming, VERY frustrating. Otherwise it still happens (if you ping -t, you'll see spikes).
6. Not tested for disabling BT.
7. Dell.
8. Intel Dual Band Wireless-AC 7260