Here is the best way to avoid traffic into Merriweather from 29...
Take 32 towards Clarksville.
Pass 29 and take the Sanner Road/Cedar Lane exit.
At the light, turn right onto Cedar Lane.
Go through 2 lights.
At the third light, take a right on hickory ridge road.
This road ends at the entrance to Merriweather. On concert days/nights, you can't go straight into the entrance, but you can go left and park at the mall.
I usually park across from Union Jacks, and go into Union Jacks for a drink, then walk over to the show. There are signs everywhere saying you can't park there for concerts, but I've never had an issue.