FWIW, you can walk inside from T6 to T7, just follow the signs to UA baggage claim. Then walk outside to the taxi stand. We called for a taxi, dispatch said 5 minutes, but is was there in about 2. Very bad phone connection. He didn't ask for our name. Someone was waiting for a taxi when we got there and one arrived almost immediately. Another person came after us and his taxi came while we were getting into ours.

I was surprised how bad traffic was to our hotel around 8pm.

Uber Black estimated around 5 minutes for curbside pickup (they're often optimistic) and about $140.