Anyone have a 17 month old going on 18 months who is hitting, biting, and pinching?

My first born went through this short phase after a bit her once and never has since. She never hit or pinched. But my son has been doing this for months now and when I tried the biting back he laughs and will sometimes cry but I don’t feel comfortable biting him. I feel like I’m encouraging him. Some people have told me to just keep biting him back others have told me to stop. Obviously I have but the biting has continued. What else can I do?

It’s pretty much the same with the pinching as well. I also gave that up. And I DO NOT HIT MY SON BACk when he hits me. I sit him down and let him throw a fit and walk away.

Am I doing this all wrong? Please help. And need advice. I plan on talking to his pediatrician when his 18 month appointment comes up.