While I do see where you are coming from, I think you are failing to see where you are headed and where Allah wants you to go. You said you have done some major sins and lost your way pretty bad, but then you started your journey back towards Allah. You have tried all the means of healing without any luck. And that everyone has failed you, even Allah has let you down. And that you are considering leaving the religion. And you don't want any advice that says have patience. That about sums it up I believe.
So here's my take on it given all that information. There are several things that needs to be addressed, inshallah i'll see if i can address them adequately.
First, it could be a punishment for all the transgression you have done or it could all be a test, a big test, to purify you from all the sins you have done. Take it either way you like. A believer always has a positive outlook and always is grateful. When he is blessed with good things then he says 'Alhamdulillah' for the blessings, and when he is facing hardship, he bears it with patience because Allah is using that as a means of purifying him of his sins. The following hadith illustrates this,The Prophet (S) said:
“Nothing befalls a believer, a (prick of a) thorn or more than that, but Allah will raise him one degree in status thereby, or erase a bad deed.” Narrated by al-Bukhaari (5641) and Muslim (2573).
and
“How wonderful is the affair of the believer, for his affairs are all good, and this applies to no one but the believer. If something good happens to him, he is thankful for it and that is good for him. If something bad happens to him, he bears it with patience and that is good for him.” (Narrated by Muslim, 2999).
So 1. a believe is grateful regardless of his situation, and 2. a believer does not despair, it's not allowed because Allah says:
“Say: ‘O My worshipers, who have sinned excessively against themselves, DESPAIR NOT of the Mercy of Allah! Verily, Allah forgives all sins. He is the Forgiver, the Most Merciful.” [Surah az-Zumar Ayah 53]
So it's not too late for you and Allah has not let you down. Rather you are letting yourself down by thinking of your Lord as such. Your hakeem was right in your misunderstanding of your relationship with Allah. It is not based on a give/take concept. Rather Allah created us solely for the purpose of worship and nothing more. And He has promised punishment for transgressors and rewards for obedience. Regardless of how one thinks of it, it's His creation and His rules. So be it your boss, your gov't, or your Creator, you gotta play by the rules and know how the system works and you'll do fine. And I agree with you on the syria example, but I guess it's a matter of perspective on that.
If you say you have been dragged through hell and back and still had tawwakkul then are you saying what you are going through now is worst then hell? If you had gone through all that and still had hope and tawwakkul then don't despair now and throw in the towel. I don't think you have understood the concept of patience. Patient are not those who say "i've waited and waited, when will Allah give me this or that" nor those who do not think good of Allah while facing calamity. Allaah has given glad tidings of three things to those who are patient, each of which is better than that for which the people of this world envy one another. Allaah says (interpretation of the meaning):
“but give glad tidings to As‑ Saabiroon (the patient).
156. Who, when afflicted with calamity, say: ‘Truly, to Allaah we belong and truly, to Him we shall return.’
157. They are those on whom are the Salawaat (i.e. who are blessed and will be forgiven) from their Lord, and (they are those who) receive His Mercy, and it is they who are the guided ones”
[al-Baqarah 2:155-157]
So while it does become hard, know that it will not stay like that forever and Allah has promised ease after every hardship. The important we have to worry about is how do we practice patience whiling going through the hardship. It helps keep this in mind:
Hadith: “Remember that there is much good in bearing with patience that which you dislike, and that victory comes with patience, and that with hardship comes a way out and with difficulty comes ease.” (Narrated by Ahmad)
For truly with hardship comes ease; truly with hardship comes ease. (Surat al-Inshirah: 5-6)
"...Bear with patience whatever befalls you...." (Qur'an 31:17) and "Be not sad, surely Allah is with us." (Qur'an 9:40)
It would help to keep these in mind as you move forward and hopefully change your outlook on your circumstances inshallah:
“If Allah wills good for His slave, He hastens his punishment in this world, and if He wills bad for His slave, He withholds from him (the punishment for) his sin, until He requites him for it on the Day of Resurrection.” Narrated and classed as hasan by at-Tirmidhi (2396); classed as saheeh by al-Albaani in Saheeh at-Tirmidhi.
“Great reward comes with great trials. When Allah loves a people, He tests them, and whoever accepts it attains His pleasure, whereas whoever shows discontent with it incurs His wrath.” Narrated and classed as hasan by at-Tirmidhi (2396); classed as saheeh by al-Albaani in as-Silsilah as-Saheehah, no. 146
Also, i would recommend checking out this link on 'Why Allah tests us with hardship" -
http://islam.ru/en/content/story/why...st-us-hardship
Lastly, this life is a trial and a test bro. You are getting your share of it, victory is promised to those who are patient. So have hope and bear it with patience as well as use this opportunity to not run away from Allah but rather to get back to Allah. If you can, consider going for umrah and drinking zamzam for it gives you whatever intention you drink it for. Also, look into how to eat black seeds to remedy this kind of ailment, black seed has been said to be a cure for all illnesses.
may Allah ease your affairs, bless you with shifa and quick recovery inshallah.
ameen.