Nick, you don't have to justify bringing anything. It is all your own choice what you bring. Personally, I could care less what you carry, since I am not carrying any of it. Remember, you asked for our opinions on your list. You are a brave man for posting your list in the first place. I don't think I would ever post my list. Not only am I too chicken, but it doesn't matter to me what others think of it. But, it is nice for a beginner to have others look at your list and make you think about it. I have taken many beginners, and usually after the trip they are ready to hear my opinions on what they should and should not take. Basically, don't worry if every one tells you to leave the zippo and bring a bic. You don't have to defend the zippo choice, just remember that most think a bic is a better option. I carry a bic (by the way) and I don't even smoke.

I have carried emergency food before. Like I said, I usually carry the small mainstay bars. They are about a third of a datrex brick. Something to think about.

If you want to buy your pack, then do it. Many of us recommend to rent first for a bunch of reasons. If you rent, you can easily find out what you want in a pack, like size and features. This way, when you do buy, you have a much better idea of what to look for. It is also cheaper in the short term, and helps you assess how much you really like this activity. If you do buy your pack, I guarantee that you will buy another one (if you continue backpacking). The same goes for tent and sleeping bag. 5lbs is pretty heavy for a tent, unless you split the weight between 3 people.
And, remind me to never, ever, ever lend you my knife. Kinves are not shovels, especially expensive knives. However, you could probably borrow Jim Shaw's. He likes his knives dull. You will use the blade on your multitool more than your BK2, especially if you dig with your big knife.
I bring an aluminum snow stake for a pooh shovel. Many here don't bring anything and just use a stick. Something to think about.
If all your food is mountain house, make sure and count how many times you use your fork or butter knife.