We didn't use the leash inside for Denna, but we did put baby gates everywhere, so she was always well supervised. When we were potty training, I'd keep her in the home office with me (a 10x10 small guest room) with a baby gate to block the door. Most of the time she spent curled up under the desk on my feet. When she started wandering around, I knew it was time for a trip outside (about every 1-2 hours). On the nipping issue - we used the "yipe" sound, like a fellow littermate. If that didn't work, a "careful" in a low growly tone like a momma dog would make would normally do the trick. Having all play-time stop, like you're doing is a great method, too. Denna is 10 months old now and has a very soft mouth. She'll still grab your hand when playing, but very gently, and if you yipe now, she'll spit it out and lick it instead.
