Router IP protection

Help me u/Daddy_Spez

I've have a VPN on my computer for years now and thought that was enough. But lately I've received notices(that I won't get into) that my Router IP has been used in malicious activity without my knowledge so now I have to add protection on that.

My ISP router is an ARRIS TG3452A and when I googled it, I wasn't able to determine a proper way of adding my ExpressVPN service on it. If I bought a router that I can put EVPN on, would I be able to install it between the coax coming in and my ISP router to protect its IP address? I hope that question makes sense because I'm having a hard time understanding this situation myself.

I just need a way to protect my ISP Router's IP address so that it can't be used for anything else other than my own gaming needs. Even when I'm away for work.