Through deliberately caused blood loss, can you balance out hypertension in an absolute emergency? If so, where on the body and how would you attempt such a treatment?

Pangolin’s absolutely right. The body will be pumping out huge amounts of adrenaline and making other compensations long before you see a drop in blood pressure. The only emergency situation in which I can think it would be warranted would be severe pulmonary edema, in which rotating torniquets and bloodletting were a secondary part of the treatment as late as the 1970’s, in very exceptional circumstances. But even then, it would be of little use and not an alternative to proper treatment. Also, that’s such a dire circumstance that the "impossibility" of medical help would look a lot less impossible.