From what I've learned about Judaism, Jews believe ...If Jesus was Jewish
There is no such thing as "Jews believe" in the sense that you can generalize something about how all Jews understand God. It's like saying "Christians believe" when we know very well that not all Christians believe the same things about God either. Besides, even what some Jews believe now about what most Jews might have believed in the past may not have any bearing on what Jesus believed -- the Jewish religion seems to have evolved over the centuries along with the religions around it. Obviously one big point of the Gospels is to show that many Jews (Sadducees, Pharisees) didn't believe in something that other Jews (Jesus and apostles) believed in.
That said, Jesus was not the only one depicted in Jewish literature as a rabbi who taught prayers that started off with "Our Father." God was always male, but the image of God as a Father figure seems to start filling in the vacuum that started when Yahweh/Jehovah lost his name due to superstions surrounding its use, out loud and in writing. That was primarily after the last Jewish writings were accepted into the OT.
If Jesus was Jewish, and evidence seems to point that way, why would he use a male gender identity to describe God when teaching people how to pray?
A reading of the OT also consistently depicts God as male, so are we to consider the entire OT as a hoax? There are a couple of hints or evidences that God revealed himself in female terms but these evidences are not popular and are not noticed easily except by scholars who tend to find a lot (maybe too much) in subtle or unique choices of wording found in a couple OT passages. Those passages are considered rare exceptions which might trace back to beliefs held by some Jews before the OT writing was begun.
Could this scripture have been altered by the early church?
Doesn't seem likely based on late passages in the OT, some passages in the Talmud, many of the "Intertestamental" Jewish writings (200BC - 1 AD). The Church would have to have changed Paul's letters too which made expressions like "to us there is only one God, the Father, and one Lord, Jesus." Paul wrote many words like this long before any of the Gospels were written.
There is an interesting theory, based on a monothestic religion promoted in Egypt, the a religion which ultimately becomes monotheistic will tend to make the primary God a Father rather than a Mother. Christianity obviously came out of a long tradition of patriarchal heritage that may also trace back to Egypt.
I posted an article related to this about 4 days ago at:
http://www.jehovahs-witness.com/12/55969/820565/post.ashx#820565 Called: "Why We Don't Call God Mother" (Subject matter is not for the squeamish though.)
Gamaliel