Hey! Welcome - yeah I have heard really good things about carpet, just be sure to get two pieces so you can switch them when you need to clean one. I use coconut husk but I know lots of people that are happy with the carpet.
About the small meal.. there is much debate on this but if at all possible it's best to try not to multi feed but rather to try feeding 1 appropriately sized meal. If petco only carries that one kind of mouse you may have to order online .. there are a few posts/links about that and try to find a place you can order a mix bag from. It may seem expensive but if you think of it in terms of feedings like I just bought a bag of six rat pups. That means I'm good for six weeks! So really it works out to be about the same as dog food almost.
Handling - it is usually best to wait 24-48hrs after eating to handle the snake they can get stressed and regurge if you don't wait long enough. A good thing to do would be to take your new BP to the vet once he goes to the bathroom (bring the stool sample) there have been many reports of pet shop snakes with internal parasites or mites or ticks etc. So it's best to get him checked out. Good job feeding F/T! That is a very responsible choice and you're lucky a lot of people have had troubles with that transition.
htt://www.arav.org is a good place to look for a herp vet in your area! Hope I've covered your questions feel free to post any others we'll be glad to help you out! and once again welcome to the forum!