According to me, I think Hinduism (in some little passageway like; i.e a little bit as grain) is not a monotheistic religion ...because of its vastness and innumerable interpretations and variety of thoughts(as if you know very well) In only some cases are their which is (unfortunately) considered in Hinduism..like for example, "Advaita" is a philosophical term used by great teacher Adi Shankar that means "not two" and there is only one God distributed in every individual which need to be identified. But, there is also another teachers (in Hinduism only) like Ramanuja, who found: "vishisht Advaita" which literally means that soul and Brahmand are not same....believing that God is different(his belief was totally contrast to Shankara) and Madhavacharya who ultimately opposes Shankaracharya's laws of philosophy and named his own as "Dvaita,which means "two".
Also,for another example: ISKCON...in Which (its my thinking)all other gods except Krishna are known as Demigods..and not equal or one.
So many differences are their as the variety thoughts are there, and only because of this,, there became a state of unmatched situations and debates which continues even today...
Hope that this will help you...!!!