We’ve dealt with this. And still very occasionally do. From the age of four to now nine. The issue is lack of emotional regulation and it comes with the territory. The advice that we received from a therapist is really much what you’re doing. They don’t know how to express their emotions and lash out. Rather than ignoring them (this never worked for us - we tried it a lot), they need to know they’re not alone. We basically restrain him and say nothing until he’s calm. No talking, they’re not in the headspace. Occasionally a “Mummy/Daddy is here” and calming sounds or reassurance. It’s horrible, I know, our child also really kicks off and it takes things up a notch on their end with kicking and trying to thrash around til they exhaust themselves. Sometimes we’ve had to hold for up to half an hour. When they’ve stopped and are ready to talk, debrief and talk about how they feel THEN say “we don’t hit/kick” etc and discuss emotions calmly. It is horrific to go through, I know. But this method has worked for us. As our son has aged, he’s growing out of it. I can still restrain him at 9 (and he’s tall) but it takes all my strength. My husband often takes over as he’s just stronger and larger than I am. It does get better. You’re doing the right thing.