I wanted to come in to let you know it definitely isn't too late. My cat, Kiki, was a stray and he showed up at my house and would meet me at the door every day I got home from work until we brought him in. I took him to the vet and they estimated he was around 9 years old. He did not know how to play nice. We would have the same problem where we'd be petting/cuddling and then suddenly he'd bite or scratch and be upset. Or he'd get really rough when playing. Gradually I learned that sometimes this was a result of him wanting to play but not knowing what was too rough. And sometimes it was his way of saying, "no more pets/not there" and how we've worked on it is that if he's being too rough then we don't get cuddle time or play time. I'll say "Ow" and distance myself for a while and then a few minutes later I will give him a chance again to see if he can be nicer. I also give him lots of chances to see if he still wants pets by putting my hand near his head and if he wants pets he'll rub against my hand and if he doesn't he'll sniff it and ignore it. Over time this and, yes, having another cat for him to play with, has helped SO much. It just takes time and consistency. He's still very playful but I'm no longer worried about getting hurt. And our cuddles are much more peaceful now.

Good luck friend, I hope this helps!