he then attempted to push me away using both of his hands against my chest
I have 2 words for situations like that: KRAV MAGA

Been practicing it for a couple of years now, and it is a fantastic way of instantly dealing with this kind of unwanted body contact.

Good for you to stand by someone being attacked.

So far I've only had to defend myself, and I often wonder the same as you, would I step up if someone else was being attacked.

Your insight is precious.