He's playing the "let's pretend this didn't happen" game. I think its normal for alcoholics to just simply view something in the past (and his jail time is now in the past) with the attitude of "let it go". Its easy to sweep it under the rug without acknowledging how their behavior effected anyone else around them.
You do have the right to say you are going to FL alone.
As far as the letter - that is up to you to decide. But you are right - make sure you are doing this for all the right reasons, not to try to change his behavior.