Your fine post struck a chord with me. I think one distinction might be that in Theravada, Thai Theravada for example, there is an adherence and emphasis on the precepts as identified in the Dhamma of the Buddha in the Pali Canon. The Canon's Vinaya ( Monastic Rules) sets out specific rules for the renunciate monks. For the lay practitioner, the 5 precepts are important, and there are 8 and 10 precept practices that involve celibacy, noneating after midday, and renunciation of the use of money, among other issues. In contrast, the Mahayana platforms do not utilize the Vinaya, and the 5 precepts, in my opinion, are seen far more liberally. In Japanese Zen, for example, ordained priests may marry, drink alcohol, and otherwise consume as the nonordained public do. I have been to Mahayana retreats where a "nonmeal" is served in the evening, sort of a way to express the fasting after midday but with a regular meal. To say the least, it struck me as odd that a sangha would pay lip service to the idea of not eating after midday, and then go ahead and engage the lips in an evening meal.
The Dhamma advises that a renunciate life is part and parcel of the Path. As you point out, the Middle Way is not one of self mortification, but of renunciation of worldly fetters such that the practice is freed of attachments to activities that do not lead to a skillful life.
Theravada is the School of Elders that practices the Buddha's Dhamma generally in the manner that was practiced 2600 years ago in the Buddha's original Sangha. Theravada Bhikkhus and Bhikkhunis live renunciate lives, with hundreds of Vinaya rules that guide their conduct and facilitate their meditation and study.
I think you'll like and appreciate the level of dedication that Theravada offers. You may appreciate the study of the Canon, which encapsulates, to the best of our understanding, the Buddha's actual teachings. You may truly appreciate learning to meditate as the Buddha instructed, and welcome the chance to learn meditation (jhana) practice in the way that the Buddha suggested to his monks.
As for lineages, you may find local to you a Thai or Sri Lankan Theravada Wat, and there may be in your locale a Wat or temple with monks from the west but trained in Asia, such as Wat Metta in California, or Amaravati in the UK. I just noticed you posted from New York: http://www.bhavanasociety.org/
might be well worth a visit, and the Ven. Bhikkhu Bodhi lives and teaches at a New York monastery http://www.baus.org/en/?tag=bhikkhu-bodhi