Unless your ex-T told you not to contact them, it is fine to make the kind of contact you are talking about. I think that they would be glad to hear that you are doing well and would be honored to know that you are using them as a basis for a character.

Unlike other posters, I don't think there is any problem with basing a character on ex-T. As long as you omit identifying details, and change some things to obscure the real person, I don't see how they could object. How closely are you going to have the created character resemble ex-T?