Well, since you said US banks, I'd just do it on localbitcoins.com, trading cash for coins in person. Fuck banks.1) Seems like most US banks cap your online transfers. I have an account at Bank of America and another at a local credit union, both of them said if I tried to buy more than $10k worth of btc on Coinbase at a time, the transfers would immediately be flagged and rejected. You need to be there in person to transfer more than that, or initiate the transfer yourself (which is not how Coinbase works). So if you wanted to make a large purchase without splitting it up into multiple smaller purchases over the course of a few days (leaving yourself open to exchange rate risk), how would you do it?
Wire transfers from smaller banks of course are your other option, and they'd want you to have an account there with the money on hand to do that I believe.
2) I'd like to move the majority of my btc into storage to keep it as an investment that won't be spent anytime soon. I tested a paper wallet and it worked fine, but I saw a post on Reddit about paper wallets being dangerous and if you try to spend anything less than the full amount of money in the paper wallet then your money gets lost (something about the way "change" works). So now I'm nervous about using a paper wallet, because when I want to eventually recover the funds, I could just enter 1 wrong number and oh look there's a couple hundred thousand dollars lost. Can you recommend the best solution? Up to now have just been storing in coinbase/blockchain.info but as I invest more it seems like another option would be better.
Like Slayerment said, there's no danger from a clean paper wallet. Everything comes back to the private key, so if you just generated the wallet and therefore have the only copy of the private key, simply store that thing offline and you've got some of the best security on the planet already.
I like to keep a copy in paper and a copy on a USB drive, hidden in separate places. (I don't trust my brain enough for the brain wallet yet.) The main thing is just to make sure that all of your keys with any considerable wealth behind them are kept completely off of any computers attached to the internet. (Cold)