For a monogamous couple, both with HSV-2, who never had an outbreak below the waist, but had outbreaks (type-2, not 1) in their mouth, is it safe, *in terms of HSV only* of course, to have unprotected sex when no outbreaks are present? Nothing is 100% saf

Most likely. It might be overconfident of me to say that neither of you could develop an outbreak if re-exposed. However, if both of you had detectable antibodies to HSV-2, it's unlikely that either could develop more than a limited outbreak in the worst case scenario. I will reiterate your statement that your question is narrowly confined to considerations of HSV only.
Preventative mens. Thereare a bunch of meds that are taken daily to revent outbreaks. Check with your doctor.
Yes. Enjoy life it is short enough. most with + HSV never have any trouble. if you have trouble there is medication to use. There are more important things in life to think about. You have a loving partner, you are blessed.