I've gotten down into the 20's with just a $7.50 walmart pad and a decent sleeping bag. No need to complicate things with the pea pod. Take the rectangle bag and if you're cold, throw it over you. The inflatable pad should keep your bottom warm.
Also, don't worry about tarp tensioners your first time out. They're generally used with silnylon tarps because they stretch. Your HF tarp probably won't.
Direction of your tarp is really dependent on the distance between trees, the size of the tarp, and how long your hammock is. I'd say just try to eyeball each config once you pick your spot and see which seems better to you.
Enjoy your first hang!