The problem is that your questions are subjective.
1. Bathing - it depends on if the dog tends to roll in things, get muddy, etc; or if the dog is a show dog; or if the dog has skin issues; or if the owner has allergies or is a neat freak or slob, etc.
2. Brushing - again it depends on the individual dog's behaviors, health, the weather, how much time the dog spends outside, if it's a show dog, as well as the owner's preferences.
3. Exercise - and again, it depends. First, most mixes have more than two breeds in their makeup. So a husky lab mix may also contain a breed that is less energetic and that trait overrides the other breeds' traits. I knew a husky- shepherd mix brother and sister. The brother looked very husky but had the temperament of a GSD while the sister looked GSD but had the brain and energy of a husky. Their requirements were extremely different.
I would simply address the "roommate" issues and leave "what the dog needs" out of it. So rather than demanding he bathe the dog X times a month, simply require him to eliminate the offensive odor. Instead of requiring the dog get brushed every day, simply make it clear that any excessive clumps of dog hair found in the apartment will be grounds for eviction. Same with exercise. Instead of requiring he walk the dog X times a day for Y minutes, make it clear that if the dog creates a disturbance or causes a mess that wll be grounds for eviction.
This makes it your roommate's responsibilty to figure out how much he needs to do to stay within acceptable guidelines.
Otherwise, you can require him to brush the dog once a day for 10 minutes, and when the dog's coat blows, you can find yourself with hair in your food and no recourse because he is meeting that requirement.