1) I don't know if temples all have it, I've only seen one, but who is the statue of on the very top of the temple? The temple where I live has a gold statue of someone blowing a horn. Who is this and why are they important?
Moroni is the statue on top of Mormon Temples.
Mormons believe that Moroni is an Angel.
Galatians 1:6-9
6I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
7Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
8But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
9As we said before, so say I now again, if any man preach any other gospel unto you than that ye have received, let him be accursed.
2 Corinthians 11:14
And no marvel; for Satan himself is transformed into an angel of light.
The Bible suggest Mormoni is really a fallen angel or a demon.
2) Why are cross symbols not used by Mormons?
1 Corinthians 1:18
For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.
http://www.allaboutcults.org/
http://www.waltermartin.com/eyewit.html
http://www.waltermartin.com/cults.html
http://bornagainmormon.com/
http://www.utlm.org/
http://www.lamblion.com