2. This gets sent to... my original addresses? An unused address in my existing wallet?
Dusting the original legacy address is the easiest way, so it also works when you import the private key. But it could be a different address, as long as you include the input.
3. Sync Bitcoin Cash Node once dust has verified on blockchain. Take offline.
4. dumpwallet in my original offline BTC wallet
Since you're using the full node, you could probably just load the wallet.dat and do a rescan.
Sounds good to me.