Just google "therapeutic relationship" but remember, he doesn't HAVE to see it the same way. He may not. It's ok to show him and explain and even to say you want/need that but it's also ok for him to set limits/boundaries and keep a distance there.
I do think having you come in today, fairly last minute, was warm/caring. There are probably other times he has said or done something that felt warm or caring, maybe write those down so you have a good reminder of those things? Maybe there is warmth, connection there, just in a different way than you are used to
Connection/Warmth can be different to everyone