1. Is the real 'Heart' in the head?

"It should be stressed here that the "heart" (qalb, dil) spoken of here is conceived of as a subtle spiritual faculty rather than the physical organ to which it is in some respects analogous, and human spiritual health is inescapably linked to this faculty of subtle perception. Fundamental to the practice of dhikr is the teaching that it acts upon the subtle heart. In its state of primordial purity the heart sees clearly into the depths of the worlds of the Spirit; but in ordinary worldly people it is disordered and its vision curtailed by the desires and perceptions of the senses and the mind. The invocation of the heart must go beyond utterance by the tongue, although long and persistent practice is normally required before that can be attained."
 

2. What are the five senses of the real 'Heart' (i.e., the subtle spiritual faculty)?

"The heart has five senses, like those of the bodily frame. Just as the soundness of the bodily frame consists in the health of its five senses whereby it perceives all the manifest world, the same applies to the (real) heart. When healthy, the (real) heart perceives with its five senses the whole of the unseen world - essences and spiritual realities. The heart has an eye with which it enjoys visions of the Unseen; an ear with which it listens to the speech of the inhabitants of the Unseen, and the Speech of God; nostrils with which it smells the perfumes of the Unseen; and a palate whereon it perceives the taste of love, the sweetness of faith, and the savour of gnosis. Just as the sense of touch is distributed between all parts of the body, that through all of them it may gain benefit from tactile objects, so too the intelligence is present throughout the heart, that it may in its entirety derive benefit from all intelligibilia through the intelligence."
 

Please note that the intellegence of the subtle spiritual faculty (i.e., the higher intellect) is different than the faculty of rational thinking and learning. The higher intellect is gifted and not learned!
 

3. How does the real 'Heart' (i.e., the subtle spiritual faculty) get involved in Dhikr?

"The subtle aspects of the heart are analyzed by Najm al-Din Razi in a chapter on dhikr in his Mirsad al-ibad: 'After that, thanks to the light of dhikr and the negation of thought-impulses, the heart finds deliverance from the turbulence of the lower soul and of Satan. It must concern itself with its own states and gain for itself the taste of dhikr. [The heart] takes over the dhikr from the tongue, and busies itself with the invocation. The attribute of dhikr will begin removing from the heart all the obscurity and veils that had reached and taken root in it owning to the workings of the Devil and the lower soul. As the darkness and the veils lessen, the light of dhikr will shine on the jewel of heart, and quaking and fear will appear in the heart: "The believers are they alone whose hearts quake when God is mentioned." Later on, when the heart is watered with dhikr, the hardness all departs from it and softness and gentleness appear: "Then are their hearts and skins softened unto the remembrance of God."'
 

Please note that when the heart takes over the dhikr, the dhikr becomes automatic. This stage is defined as 'ajampiya jamp' in the ginanic literature where the invocation of the bol (Ism-i Azam) becomes automatic. Real spirituality begins when a person reaches this stage in his/her bandagi (meditation).
 

4. How does dhikr get established in the innermost secret part of the real 'Heart' (i.e., the subtle spiritual faculty)?

"Najm al-Din Razi goes on to explain how further progression leads to the establishment of the dhikr in the sirr or innermost secret part of the heart. Once thoughts of and attachments to created things are eliminated, "the Sultan of Divine Love" descends to subdue any remaining unruly elements in the soul, to purify "the City of the Heart", and install the virtues therein definitively. The heart now finds true joy, and God's Command holds sway over every attribute of the seeker's personality and every action of his limbs, in accordance with the Sacred Tradition quoted above."
 

(Source: ¹Muhammed Isa Waley. Contemplative Disciplines in Early Persian Sufism. In: The Heritage of Sufisim. Volume 1. Classical Persian Sufism from its Origins to Rumi. Edited by Leonard Lewisohn. 1999. Oneworld Publications, Oxford. Excerpts taken from pages 528-529.)

"The true believer is one who has no malice in his (real) heart, which is pure. Whoever wants to attain my didar in this world and the hereafter, must keep himself away from every defect, opposition and evil act. And according to how far he achieves purification of his (real) heart, and is able to see his Creator in this world, so he will also see Him in the hereafter. It is obligatory and necessary for the true believer to recognize his Creator who is manifest in this world in the form of a human being, and to see Him here in order to see Him also in the hereafter."

(Source: Imam NOOR Mowlana Shah Mustansir bi'l-laah II (a.s.) in Pir Pandiyat-i Jawanmardi, pp. 62-63)