1. What if I hadn't printed this sheet? Like, if I were out of printer ink or something... would I have lost access to the key associated with this address forever?
Afaik on blockchain.info it only shows you all adresses you have on the blockchain.info wallet. So they would still be there.
2. What would scan these QR codes, and when would I ever scan them (assuming my intent is to save BTC, not spend anytime soon...)
You can scan them with a smartphone app, there is a QR code for the Bitcoin address (to receive) and for the private key (to spend).
All the QR code does is saving you the time to type those.
3. Is scanning just an alternative way to access the key/could the key be used without the scan?
yes
4. Am I correct that the tiny series of numbers/letters etc beneath my BTC address is the key?
Probably, Bitcoin addresses always start with "1", private keys always start with "5".
5. What is with the two-step verification? Is that necessary when I'm not spending? At what point is that relevant?
It's an additional security feature to the online wallet. It makes spending your Bitcoins from there way more difficult for an hacker.
6. I'd like to choose a seller on localbitcoins w/high feedback, etc to buy a small amount of BTC from today. I know that'll mean going to a bank, etc - I've been reading through the different sellers' requirements, etc... but am I ready for this step, or would I be risking losing $ because of the fact that I'm not really understanding the whole "key" process/paper wallets, etc?
I think you should at least understand private keys, that's kinda important. I guess high frequency sellers there are probably used to answer a lot of questions, so maybe you.
7. So my private key is sitting online in Blockchain, essentially, because it came from my wallet... right? So... oh, forget it... I'm just SOOOOO confused.
Try this explanation: It's just like a key to a vault. If you want you can copy those and have multiple of the same key on different places.
Wallets like blockchain.info manage (/hold) those keys for you.