First of all... if you bought one of those zoo med heat pads, you will want to get a dimmer switch fo some sort so that you can control how hot it gets. Mine actually got too hot to touch when it was just plugged into my wall.

You will want your tank to be about 92 on the warm side and low 80's on the cool side.

If cared for correctly, your snake should live to be 15-20. judging by its size it seems to be only a few months old at the moment.

As for frozen or fresh killed... Whatever is easier for you. I have heard that frozen kills some of the vitamins, but i dont know if thats a solid fact or not.

Easiest way to reheat frozen is to put it in warm water (not hot) until it's soft and warm to the touch.