My goal is to create a completely anonymous, reasonably secure bitcoin wallet.
That's a very ambitious goal.
Complete anonymity is difficult to accomplish.
To the best of my understanding this will allow me to have a completely anonymous and secure storage of bitcoins,
I'm not convinced that bitcoinfog is beyond the ability of forensic accounting software to link the source bitcoins to the destination address. Keep in mind also that when you send the bitcoins somewhere in the future, the person/company that you send them to may be able to identify you. You then have the possibility of one person/company that provided you with bitcoins in the first place knowing something about you, and another person/company that accepted the bitcoins from you knowing something about you. With some forensic accounting and enough time and computing power, it may be possible to link your initial receiving address to your cold storage address to your eventual "spending" address.
the only bitcoins that I could possibly lose are those in whatever wallet I import into Multibit in the brief window before I send them out.
If you're really worried about that you can use software to generate the rawtransaction on an offline computer and then transmit that rawtransaction from an online computer.
Does anyone see any problems with this plan or why it might not work?
Obviously it is important to keep the paper wallets secure from loss, damage, and theft.
1. If I generate a bitcoin paper wallet at an offline computer, I don’t need to take it online in any way until I want to withdraw the bitcoins, right?
Correct. You don't even have to take it online to "withdraw" the bitcoins. You could create and sign a rawtransaction offline and then safely take just the completed transaction online.
I can just send the bitcoins to the public address and they will be waiting there for me until I import the private key into a bitcoin client?
Correct.
2. I read that configuring Multibit to work anonymously through Tor is as easy as pointing it to the Tor proxy. Is that true? Any security issues involved?
I'm no expert in TOR, but it is my understanding that if you are not careful, it is possible to leak your identity. Some common leaks are javascript, DNS lookups, Adobe Flash, and cookies.
I've never tried running MultiBit through TOR, so I'll leave that question for someone more knowledgeable than me to answer.