When It's Not All Rainbows and Unicorns

"How are the dogs?" my mom asked over the phone. "They're fine", I answered, "Mushroom hasn't had an accident since her first day."

Wasn't me - the other dog did it

Okay, so I fibbed because I didn't want my mom to be worried. Mushroom may have succeeded with housetraining, but the dogs are anything but fine. It's been two weeks since their first meeting, and their interactions with each other leave much to be desired.

When they are playing with each other, we have a hard time getting Badger's attention. We can call Mushroom away and make her sit for a treat, but Badger will continue trying to play with her. Additionally, bowling-ball Badger is considerably larger and tougher than the petite Mushroom. He easily knocks her over and proceeds to stand on top of her, while she's reduced to gnawing on his ankles. Since he doesn't listen to warning growls, she has started biting him to get him away from her. While these bites have not broken skin, they have torn out small clumps of his fur. The other day, a bite from Mushroom aggravated Badger enough to start snapping at the air. Since then, we have stuck strictly to crate and rotate.

Two seconds later, they were fighting again

We're quickly running out of ideas, but here are the ones we haven't tried yet:

1. Use extremely high-value treats, in the hopes that Badger will respond consistently when we call him out of play. Badger has gotten less treat-motivated in the past few months, though.
2. Buy a baby gate to allow them to both be out but not playing. Neither of us has any idea how to train dogs to respect baby gates. Also, the dogs are already capable of being quietly crated next to each other with little effect on how well they play together.
3. Go back a step and only allow the dogs near each other if leashed. Badger pays much more attention to us on leash. The downside is that they cannot play at all on leash, because their leashes get tangled, and Mushroom gets upset.
4. Hire a professional trainer. We've been holding off on this option because of the cost involved, but we know this is our best bet. I did a trainer search on the APDT website and am going to start contacting trainers over the weekend. A private session looks like it can range anywhere from $50 to $250, depending on the trainer and the location.
5. Finally, if all else fails (or if we run out of money to pay trainers), we would put them permanently on a crate and rotate routine.

 Has anyone faced a similar situation? Has anyone tried any of these tactics? And last but not least, does anyone have comforting words or a success story?