I guess happiness is just a figment of ones imagination
According to your account, you had 3 years of blissful happiness with your now ex-dp. Was that a 'figment' of your imagination? If not, some would say that's not a bad innings in the quest to find lasting happiness which, in itself, can only come from within rather than being a quality that is bestowed on us by another person.
You've done the honourable thing by falling on your sword, OP, and in that act alone you have nothing to reproach yourself for. However, if your ex verbally lashed out at you in a manner that "reminded" you of your previous/former ex it could be he's not quite as saintly as you've portrayed him to be and, as it would seem he's been "unhappy for some time" but was too cowardly "couldn't tell you this", you did well by not asking for another chance as a refusal would have inevitably made you feel infinitely worse about yourself in the longer term.
If, as I'm beginning to suspect, the man you've idolised has clay feet, it may be that the "love or warmth" you hadn't felt before was little more than control masked by what appeared to you to be kindness and concern for your welfare. I'm curious to know more about how you came to stay out on the fateful night when "he would never let me go out but this once in a blue moon". Who initiated the argument that led to him going home without you?
Some use others as a means to an end and, if he had issues with his family prior to meeting you, it could be that he used you to say his long overdue goodbyes to them and ingratiated himself with your family in order to exert greater control over the exceedingly grateful and increasingly reliant you.
You've said his friends became your friends and, if you were only able to go out "once in a blue moon", you would have had little opportunity to make new ones. If that's the case, it's unsurprising that you've kept in touch with your old, some would say undesirable, pals.
Am I being fanciful? If his friends are being 'spiteful' to you (using what means?) within such a short time of you having confessed all, he's been remarkably quick off the mark in spreading the word and, to my mind, that is very far from being the mark of a gentleman.
It seems to me your problems stem from an unhappy childhood with an overbearing father which has led you from one abusive man to another, and I'm yet to be convinced that this last relationship was the idyllic meeting of minds you appear to believe it was.
With regard to your df's decree that you must be cast out leave his roof by the end of the month, by my reckoning you've got 3 days to find alternative accomodation. Do you have sufficient funds to achieve this or do you have another relative, a friend who's not into drugs, or a colleague who can offer you a temporary home until you can find something more permanent?