Going back to the original question for a minute.
Judaism, Christianity and Islam are called the Abrahamic religions because followers of these religions see themselves (either literally or metaphorically) as being the 'children of Abraham' - those millions of descendants promised by God to Abraham in Genesis. All three religions hold the Old Testament/Hebrew Bible to be holy. For Jews, the Torah, the first five books, are the central scriptures.
Judaism, Christianity and Islam are monotheist faiths. There is only one God, who is the creator and sustainer of all things. It's not a question of choosing one god from among all gods, because there are no other gods. As Muslims say, there is one God, who is God.
However, the three religions see God differently. The Jews were the first people to discover monotheism, and the Hebrew Bible is the story of that revelation and the struggles of the Jewish people to live as God's holy people. It's a story of God's enduring promise of faithfulness despite human forgetfulness and unfaithfulness.
Christians believe in that God and believe that they too are part of God's promise. They believe that God renewed his promise by being born as a human, living a human life, teaching about God's kingdom, choosing an undeserved death and being resurrected. For Christians, God reveals himself most fully in the birth, life, death and resurrection of Jesus. But he also reveals himself in the Holy Spirit, who makes a bridge between heaven and earth. So for Christians, there is only one God, but God is made up of three persons - three in one.
Muslims believe in the same God, but for them Jesus was not a revelation of the divine self but one in a long series of prophets who told people about God. Muslims believe that all these prophets (many of whose writings are found in the Old Testament/Hebrew Bible) were leading up to God's final revelation, which was given to Muhammad. These revelations, the Koran, are sacred to Muslims because they contain the direct word of God.
So you have a paradox. All three religions believe in one God. Some followers of each religion believe that their conceptions of God are so different that the God of the others is, effectively, not God. This is particularly true of some Christians, sadly. Others (and I am one of them) believe that if there is only one God then logically we are all worshipping the same God. As a Christian, I believe God revealed himself in the life, death and resurrection of Jesus. How all three conceptions of God might be true is a paradox - something that I might never understand fully. I'm content not to understand it and to live with a certain amount of uncertainty without needing everything to be absolutely black and white.
The question about suffering is a good one, and perhaps one for another day - I've got to do some work now. But I would say two things for now. Firstly, it would be a very human-centred view of the world to demand that God only create things that didn't harm humans. If God is the creator of all, then surely he loves mosquitoes, worms and viruses as much as he loves us? Isn't it a bit childish to think that we shouldn't suffer at all? Secondly, if suffering is part of life, then the question isn't 'why should we suffer at all?' but 'how can we cope with it?', and 'how can we take responsibility for our part in it?'. There are many answers to these questions, but the great religions of the world have tussled with these questions for milennia and their answers are worth looking at.