Very red inflamed skin w endless acne cysts for 15 yrs. Sometimes 20+ cysts in face at once. Finally clearing. Could this be from bigger health issues?

See a dermatologist. Your acne is hormonal. Do you have normal menstrual cycles? Birth control? Some birth control makes acne better, some make it worse. Spironolactone at 100mg a day is probably where you should be. If not responding after a few months, isotretinoin orally for 20 weeks will rescue you. No acne pills should be used if you are pregnant.
Yes. Acne and acne type rashes can because by many systemic illnesses and other problems most the time acne is isolated issue.