I think you should tell him, if you haven't already, that you think it helps you when he loosens the boundaries. I think another way to understand countertransference is that T's do use who they are and how they build relationships in the therapy room. Maybe in some ways that is the only tool they have. But what you notice in terms of how the relationship goes and how you feel is really important information. I think it is progress to notice the connection you have.

I also think that T's are good at finding the likeable things about clients and focusing on them. I often work with people who have experienced lots of trauma and often times they disclose that they have or have never had any real friends. And these are some of the most charming, disarmed, and interesting people I have ever met, and I enjoy working with them so much. But, truth is I probably wouldn't have independently sought them out for long term friendships, because I also see the problems too. I can understand their deficiencies (it is related to the work I do) while also engaging them with their strengths.

So I think what you are noticing is not that your T likes you, but that he is bringing out, in a relational way, the most likeable things about you. This means you are likeable, and it clues you into how you can engage others in the outside world. Maybe it also shifts your understanding of how others like you too-- and I think it is not what people do. I don't think these objective things you point to-- the extending of sessions, self disclosure, etc-- is evidence of your likeability. Just like friendships in the outside world are more often constrained by life circumstances/time/what's going on with the other person, not how much they like you. My best friends are people with full lives and take care of multiple people-- children, elderly parents, entire organizations, etc. They don't always have time for me in the way I'd like, or that they'd like. It isn't a commentary on my likeability.

I don't have any doubts, ten years with the same therapist, that he likes me. Because I don't doubt that I'm a likeable, even loveable person-- as is every person on the planet. And I know what makes me likeable in therapy-- I take risks in talking about tough things in tough ways, I go for my own jugular, and I am brutally honest about myself and willing to look at myself in pretty unflinching ways. And these are also qualities that the people (well, most of them, family is not so crazy about this) like in me as well.

I think it's possible that causal connection in what you describe is rather circular: when you open up and share yourself more, your T does as well. When he opens up more to you, you open up more. Lather, rinse, repeat. Keep doing it, and so will he. Sounds like you're on a roll.