You can send as many coins to your wallet as you want. In my opinion, the best way to run masternodes is to create separate addresses for each. And yes, you can run as many masternodes as you want on a single wallet.
In short, your local wallet's desire.conf should be empty. To create a new masternode, create a new address, send exactly 1000 DSR to that address, and then, do all other stuff related to masternode.