If you have no medical reason for blood thinners, it's better not to take them. Or maybe just one baby aspirin per day. You only need them (badly) if you get Covid-19 and then go into cytokine storm.

Vitamin D, quercetin, and zinc I would recommend highly for everybody every day. Even if you don't catch Covid-19, those are going to help against the flu and colds. Oh and the Vitamin D is good for little stuff like cancer, heart attacks, autoimmune diseases, etc.

You are absolutely right about isolation: Even young asymptomatic cases can get permanent lung damage.