Nirvana is not Heaven. Thus, I repeat, Buddha did not believe in Heaven. He also did not believe in God.
One true God, one Heaven. No admittance for those who do not believe, and that's what God has to say about Himself and His home.
Buddha advanced the concept of some perfect human, as in an elaborate form of humanism. Become ever so perfect as "being" (a human) and become Buddha, find oneself by losing oneself in Nirvana, a state of humanism.
There is no room here for "moral equivalency." Nirvana is not a moral nor theological, nor faith principle equivalent of Heaven.
No he didn't.
He advanced the concept of the perfect soul that wouldn't have to be imprisoned by the corporal.
In other words, an angel.