Bus likes cats, and loves kittens who are walking around age (he is a little predatory toward tiny kittens (<4 weeks) until they walk like normal cats and lose their squeaky meow). He gets SO excited by them though that he tends to overwhelm them if not reminded periodically to give them space. I supervise closely, and call him off and put him in a down (he actually will play while laying down often on his own) if he is getting too excited or they are looking like they want to escape. If the kitten comes back for more, or is equally involved in the shenanigans, I let them go. It works out that as the kitten gets bolder and more skilled at the game, I let him have more freedom in their play, and just keep an eye to make sure no one gets in a tight spot. His most recent kitten is now a 2 year old adult, and not as keen on playing with him these days, though I credit playing with Bus for his mostly nice adult behavior
There are a couple videos in this thread (toward the end) of Bus playing with Jackson as a kitten of various ages. As you can see in the more recent vids, they could get pretty rough, but if it is mutual, no harm, no foul. My 3 cats (Jackson lives at my parents' house) are all pretty dog friendly as well, and as you can see, there is always some kind of dog/cat cuddling going on in my house
They get a little offended when he tries to play with them, as they were raised with a dog who was tolerant but more or less ignored them, or would lay with them, but never played. https://www.dogforum.com/general-dog-...affair-272226/
Because of the size disparity between a springer and cat, I would be inclined to separate when you aren't able to supervise, or at least make sure kitty has ample places (high and low) to escape in case things do get too intense, but it sounds like things are on the right track. My guess would be that with time, both will settle down a bit and just become buddies, rather than constantly wrestling around (though my childhood cat and dog would play/roughhouse as adults). Enjoy it while it lasts!