Why do you answer a question with a question?
Shouldn't you first answer my question then ask yours?
But as you dont want to I will still answer yours.
You need to read verse 13
Who was (before) a blasphemer, and a persecutor and injurious, but I obtained mercy, because I did it in ignorance and unbelief.
All past tense
So in verse 15 he is simply stating the person he has been explaining previously. He is Paul who previously lived as described.
The idea Paul the christian was the worst sinner on the planet doesn't bear credence in my view
If Paul wasn't a sinner he would have said so. What better way to encourage people than to say, 'I used to be a sinner, but GOD changed me and I'm not any more.' But he didn't.
