meaning "Truth is me" or "I am God"
It is 'i am the truth' or 'i am on the truth'. Not "I am God"
"In my turban is wrapped nothing but God,"
There is nothing in mind by God.
"Maa Fil Jubbati Illa-Allah" meaning "There is nothing inside/underneath the cloak except God."
There is nothing inside me but god, or i am at one with God.(Not God).
He is much understood, as he was in his days. Sufis use of language is a science in itself, that does not lend itself to an easy understanding.
He was not a heretic but an obsessive Sufi, who thought about nothing but God. His was a sorry end largely because he deliberately refused to dispel the suspicions surrounding him, which he hoped would make him a martyr.(A bit twisted if you ask me)
SIDE NOTE: A lot of latter day Sufis also stand accused of ascribing miracles and acts, defying both laws of physics and common sense to personalities associated with Sufism. As proof of the special favor gained through the closeness with God, that can supposedly be achieved by Sufi mysticism.