No they cannot...I think..correct me if im wrong
At the moment, since your 1000 XC will be fragmenting and moving from address to address all the time, you won't be able to isolate your other balances from the coins you use for mixing.
So you'll need to keep a personal wallet.dat, and a separate wallet.dat for a mixing node.
You're right that coin-age will reset all the time, and so you won't stake your 1000 XC. It will be more profitable to use your 1000 XC to trustlessly forward transactions.
I don't have figures on what the revenues will be at this stage. We'll release those details soon.