So I have two boys, got the kitten when my other cat was a bit over 1 year old. The initial plan was to do the proper introduction with keeping the kitten in one room, then introducing through glass door first etc but that went out the window immediately since my cat was too curious and clawing at the door where the kitten was. We actually ended up just letting them meet each other immediately. There wasn't any hissing but my older cat was freaked out, scared at first, then attacking the kitten. Then for the next few weeks/months (can't remember) it was the same as with yours, he was playing so rough with the kitten! He was also grooming him sometimes but mostly attacking him at every opportunity. We were only really intervening when the kitten was meowing when being attacked or it was just getting extremely rough.
After a while, the kitten got slightly bigger and they are good friends now. They both attack and chase each other. The kitten is still much smaller than the big boy tbh but they play together. So it definitely gets better. It doesn't sound like there's anything to worry about with your cats.
It's only week 2 for you and it sounds like they are just playing so try to supervise them as much as you can and maybe intervene if it's getting very aggressive. If they're playing,cats usually tend to stop every so often to take a breather. If it was a proper fight, they wouldn't be stopping and it would be escalating, i think.
Some of my friends cats didn't get on for about 6 months and were fighting to the extreme and now are great friends, so I think you're safe with yours if they're already not too bad after a couple weeks. Your boy is probably just trying to show who's the boss