Those are good questions, although the last one is a little confusing. I talk about positive and negative pantheisms elsewhere (when I criticize some uplifting kinds of pantheism). I don't see why there need be only one kind of pantheism. I interpret things in a way that entails cosmic horror, but philosophically minded folks are free to see things differently.
Schopenhauer's Eastern pantheism entails horror because his divinity is a blind, impulsive, amoral monster. That's close to my view, except that I don't personify the cosmic whole by thinking of it as a will.
Is human alienation a delusion, given pantheism? I don't think so. The alienation is realistic, not delusional; on the contrary, the myths and conventions that please us are more likely to be delusions. Nature divides itself as it decays via entropy, and this is apparent in the evolution of intelligent, self-aware, social mammals who recognize eventually the absurdity of their predicament in an uncaring cosmos. Nature is divinely creative, but not perfectly moral. So divine reality needn't be comforting to social beings.
