mrt144,
It would seem that you need to continue to build on your 'pluses' with tactics such as; change to his favourite civic, swap to his religion, share a long war, gift him resources or technology, etc. as well as addressing the negative by ensuring that you have indeed cancelled any deals that you might have with his worst enemy. The negative trading modifier will eventually decay away, but sometimes it can be painfully slow.
I must say that I'm no expert on Permanent Alliances, however you need to share a long war or share a Defensive Pact for a while (the Defensive Pact will also require 'Friendly' for Augustus Caesar according to ori's reference) for the Permanent Alliance to become an option.
Finally, the title is "Need to get a Permanent Alliance for domination win" ... can't do it by yourself?