I had this very same thing happen to me, except for the spitting part. I rough-house and tickle my SD6 and one day out of nowhere she bit me. Now as long as this isn't a habitual thing for him to bite people, which could be a sign of a bigger issue, then it's probably most likely the same reason I discovered. I researched older children that bite and came to find out that there is a reason why they do this. They do not feel safe and secure with the rough-housing. Their defenses come out, so they bite because they know it hurts you and it's a way to get you to stop. I no longer engage in wrestling/rough-housing with her anymore, needless to say. I was very upset after this happened and SD6 apologized to me for 4 days in a row. lol She knew she messed up. I have slowly gotten over it and have tried to realize that was her way of telling me she didn't feel safe with us rough-housing. I told her if she EVER bit me again that I would spank her myself and I told my SO this as well.

This is why rough housing can be good, the child learns how far they can go, if you see lion cubs playing with their mother, when they get too rough Mom will swat them, I rough house with my sd6 and she loves it, I think it toughens her up as well, I don'nt want her to be too much of a soft girl lol, your ss got carried away, he should be punished as spitting and biting is disgraceful, he's learning how to act appropriately, as long as he acknowledges that this behaviour is unacceptable and apologises, just move on, as for Mothers Day maybe it would be better to celebrate it another day when you have more time and are in a better frame of mind.