Yes, there are many Jews who are agnostic or even atheists.
Some do, some don't. Not all Jews are loyal to Jewish tradition.
"Allah" is the Arabic word for "God".
That presumably being the 'Three in One, God' - Father, Son and Spirit. Some do, some don't, some doubt there is a God, some do not believe there is a God.
Some of them were!
Some Jews are Christians but most are not. It is because Christians believe that Jesus is the son of God, the Messiah, who died as the lamb of God, a sacrifice for all who believe. Jews do not believe this.
God will curse those who curse the Jews
No. The kippah is a reminder of God's eternal presence. Some Jews also see it as a separator between themselves and God, or a sign of respect for God.
They did not doubt, no one was privvy to the plans.
Jews believe in God the creator and in the Torah which God gave.
Some of them look like people worshiping God and some of them look like they think they are worshipping God.
Jews pray to God
Jews believe that God did everything it says He did in the Bible - including creating the entire universe in 6 days some 5780 years ago. God also continues to keep the universe in existence.