Cat and Rabbit

So, my roommate has a rabbit and she and my kitten are very good friends, they play and cuddle all the time but I am getting cornered that as Shadow gets older he might hurt the rabbit with rough play or the rabbit might hurt him in self defense when they play. He has been kicked a few times although never hard already when he gets on her nerves and then we separate them and give them cool down time. Is there a way I can get him to be less rough with the rabbit so that neither of them get hurt. It's great when they interact but its a natural fear. Especially with recently where the rabbit is asserting her dominance on him by pushing him to the ground and humping him lately. 

I wouldn't worry about the cat hurting the rabbit. My family kept outdoor rabbits (free range in the daytime and caged at night) for years with our cats. They usually developed an inter-species understanding all on their own. I would recommend spay/neuter the rabbit and that might help with the humping (not to mention rabbits have a high rate of cancer and you can help reduce chances by fixing them). It's probably good to separate them to prevent injury when they go at it but you want to let them figure out boundaries too so don't separate at every instance; just when it looks like it is getting too serious. The rabbit will defend itself if needed and they can be nasty if provoked (big teeth=big wounds).

One of my rabbits used to charge at the cat and chase him around the yard. She'd go straight at him and he'd go straight up in the air. Then she'd flop out and pant for a while before falling asleep. At which point the cat would sneak back in the yard and glare at her. It wasn't constant or anything but often enough that the cat looked around for her before relaxing. 

Our dwarf Rabbit is 6 years, about the size of a 4 /5 month old cat. He has been introduced to may cats and kittens ( we have 7) he can give most of them a run for their money but I always watch for the first few weeks to see how they do. There has been games of tag, chase and some inappropriate sexual interest but we really only have one cat that would really like to eat the bunny and he probably whould get hurt if we left them alone.