Since each of the main branches of Abrahamic religions could be described as Judaism, Islam and Christianity, then what are the unifying beliefs over and above monotheism?
What combines them and then what are the prophecies that each share?
Meaning what is the missing link to combine the beliefs/people?
This seems to me a kind of odd way of putting the question. Both Christianity and Islam claim to be fulfillments of the Hebrew scriptures; they both specifically and repeatedly reference these scriptures, so it's not like there is some great mystery as to the "common link".
As to the content of that link, what is most fundamental, what makes it unique is a corporate idea of salvation, i.e., that salvation is ultimately seen in a "people", however defined. And so you have cognate terms like "chosen people', "kingdom of heaven", "body of Christ", "social gospel", "ummah", etc.
What fundamentally distinguishes them is that first of all Judaism is a universalist construct with an ethnic practice, while Christianity and Islam are universalist both in construct and in practice. This universalist practice naturally entails a basically absolutist ideology for both Islam and Christianity.
The fundamental distinction between Christianity and Islam is that the former stresses doctrine (the creeds) and the latter practice (shariah). Either emphasis, however, serves the same universalist ideology that can be turned to a great variety of ends.
As for claims and counter-claims: the Christian claim on the most general level is that fulfillment of the law paradoxically also involves a rupture, a metaphysical/emotional/mystical transmutation. The Christian claim therefore is that the Jews don't know how to read their own scriptures. The Jewish response: good grief!
The Muslim claim, on the other hand, is not metaphysical or emotional but essentially legalist. They go back to Abraham, they say, because the Jews have not lived up to the original injunctions of God. The Muslim claim, therefore, is that the Jews have garbled and ignored their own scriptures. The Jewish response: good grief!
Such is my contribution to interfaith dialogue!