Yeah you have to hold the back button in safari and choose the last page of you don’t open in a new window. I hate sites that jack your back button like that. Normally they end up blocked in my Pi-hole. Reason they do that: bad coders using cut and paste code or a framework they don’t understand and think it will help users navigate their site easier. Had a teacher go off on how this practice should be illegal like un-closable pop ups.
I added my domain and have never had it marked as spam at any major email provider, only a few small, self-hosted servers and that was probably due to misconfiguration or high spam sensitivity. See if this might help you out.