AFAIK, lead in leaded solder is dangerous not for the fumes it provides but because it leaves contaminants in the environment. As long as you keep leaded solder in a dedicated work environment, always wash your hands before leaving it, and don't ever bring food in, AFAIK it's genuinely safer than the flux.
whereas the flux is dangerous _fumes_, AFAIK air pressure is enough to prevent leaded fumes from being super dangerous [in amounts used by normal people, at least.]