I don't get it? You were having 10+ shot rallies down the line to each other and you couldn't step around and hit a forehand?
I think it comes down to anticipation. Tennis at that level is like chess. You take some calculated risks to tilt the game in your favor. He probed you and found that he wanted no part of your FH. So, what did you probe of his game?
For any lefty, a no brainer for me to think of is a slice serve out wide to a righty backhand. I'd perfect that serve and get used to stepping two quick steps to your right for an inside out FH to the open court. That type of 1-2 punch combo puts you in control of the point. Once you are in control, the angles are up to you.