Honestly you can’t make anyone to spend more time whth you, connect emotionally and have sex, then you either have to accept thats how your life is going to be or move on and find a better match.

If the guy isn’t interested in planning good time with you and have intimacy at 27, then I am not sure why you think he’d want it at 28? I’d not be sending him letters. He isn’t going to be all different becayse of a letter

For whatever reason he just isn’t interested. You are only 25. You don’t need to be tied up to a guy who isn’t showing you any kind of interest. You can have a clean break and find a better match