You are absolutely right, and this is confirmed by Old and New Testament Scripture:
...I believe the Messiah will come...
Yes, indeed! The fact is, He has come but also will come again (known as the Second Coming). Jesus Himself says this, as do many other Scriptures.
...I believe he will be a righteous human,...
Again, correct. There was only one "righteous human", Jesus. "Righteousness" can only be imparted to others by His gift, His blood, His actions...
...not a god or aspect of God...
You nailed it again! He is not "a god" (small "g") nor an "aspect of God". Jesus is fully God and fully man.
...I don't believe he will be killed by God, nor anyone else....
Again, you are right on target. His death on the cross was a one-time event, and He is now resurrected for all time. Death could not hold Him, and was a singular event for a singular purpose - our redemption!
And when He returns, He will return as you envision Him - as a King, leading His armies and His People to reign for 1000 years (check out the Book of Revelation, especially Chapter 19,20) before His final victory over Satan.
So, you aren't at all wrong or in error of what you say. You just missed out on His First Coming, which ushered in the Age Of Grace. But, you can still fully partake in it as well as the Second Coming.
The Messiah is for all mankind, not just the Jews. And the sin of all mankind put Him to death, not just that of the Jews. It pleased God to use His special, chosen, faithful People - the Jews - for His sovereign Purpose.
We Gentiles have much to thank you for. Please don't let a one-dimensional view of all this keep you from partaking in His Kingdom in this present Age Of Grace. There are many Jews who are also Christian. Being such does not make them less a Jew.