I understand what you’re saying x. But in his second inaugural address, Lincoln said, “Let us judge not, that we be not judged.” Those are the words of Christ, which are very New Testament.
The fact that someone quotes from Scripture doesn’t necessarily make him a Christian. Certainly Lincoln, like everybody in his time, was influenced by Christianity and the Bible, it was inevitable. The question is, was Lincoln personally a Christian believer?
Most of the testimony we have from those who knew Lincoln earlier in life was that he was never a Christian believer, but they didn't have much contact with him in his later years and simply assumed he didn't change.
My understanding is based on Allen Guelzo's idea of Lincoln's "Calvinized Deism." You could read his book Abraham Lincoln: Redeemer President and see if you agree.