It went really really well

I walked in and he asked me how things were going, etc. I was like "so if this was a videogame and there was a series of levels to get through or obstacles to pass before the end, there's one more that I haven't talked to you about."
I told him I had written stuff out for him to read. He suggested I read them. I said that that would absolutely not happen, and his two choices were either that he read the papers while I sat on the floor on the other side of my usual armchair, or that he would not read the papers at all and I would throw them away and not discuss it. He agreed to read them, though he clearly thought it was a bit silly/melodramatic (not in a mean spirited way)
At some point he asked if we were going to be able to talk about this after. I asked if he'd read to the end yet. He said no. I said we could talk about it after he finished reading it. (at the end was the part about understanding if he didn't want to or didn't think he should continue working with me)
He finished and then said he'd thought I had some questions for him and I was like "no, not really."
He said he didn't feel the need to discontinue working with me because of this. At some point a bit later he said something along those lines again, and I asked him if he was really sure (I'd asked in my note that he make sure he was really sure because I would much rather it happen now than later). He said yes. He thanked me for communicating about this with him. He said he thought this kind of attachment was understandable given what I lacked at certain points in my life.

We got on the topic of boundaries (I'd highlighted some of the article talking about boundaries being important, so this wasn't him just bringing it up out of nowhere). I explained my situation with my last therapist who was a really sweet lady whom I really like, but who crossed a lot of boundaries with me and told me I was "special" and that she loved me and how that felt like a responsibility not to let her down or to disappoint her, and how her not maintaining the boundaries made me feel like I had to constantly be thinking about the boundaries and what would be crossing them and what was or wasn't okay, because she wasn't maintaining them.
I also told him about how I'm really good at getting people to cross boundaries for me. It's hard to say without sounding like a narcissist, but my high school teacher who I developed a kind of attachment fixation on from afar and whose approval I craved? By a year or two later I was at his house drinking and smoking illegal plant matter with him and his wife. The chemistry professor I developed a kind of attachment fixation on from afar? That was 4 years ago, and for the last two years since I moved away for grad school he has has texted me "good morning sunshine" and "goodnight. hugs and love." almost every day (and apologizes when he occasionally misses it, like if he falls asleep on the couch), and before I moved we hugged on a daily basis, he'd taken me to the ER when I needed stitches for SH, he'd let me fall asleep on his shoulder.
Teachers throughout my life have talked to me more like I was an adult, and expected me to be partially responsible for my twin brother. I knew all the teacher gossip as a high school student. I knew details of some teachers' personal lives.
So yeah, people cross boundaries for me. And at the time it makes me feel "special." But it's also a responsibility.

At this point my therapist pointed out that kids need boundaries and, while they may not always like them, they keep them safe. He also made a point to say that it wasn't my fault that other people crossed boundaries with me, because I'd said that something about me makes other people cross boundaries. He told me it would be his job to maintain the boundaries and that I could trust that he would. He understood how important that was so that I could feel safe. I believe him. I asked him if he'd ever been rock climbing (he has, but only indoors), and compared it to climbing up the wall, being responsible for holding on the entire time and not slipping, getting up to the top and clinging on to the wall, and the belayer says "okay, now let go." He said it was a good metaphor. I told him I hoped he was a good belayer.
He noted my expectation in my writing that my attachment to him would grow in intensity. I confirmed that. He said that he hopes that if/when that happens that we can talk about it openly.
Last week I asked if I could show him my arms (scars) and we talked about it and in the end he said no because he didn't want to give them that attention. I was understanding, and I actually think he made the right decision and appreciate that he did. He asked about my response to that, and added that he'd worried after that his use of the word "attention" might have a negative connotation (he thinks about me outside of sessions! At least for a few minutes directly after lol). I explained why I'd thought he actually made the right decision and how I appreciated it intellectually, but that emotionally I had not responded well. That it is often the case that something will happen and rationally I'll see the situation clearly or be more reasonable, but that emotionally I'm reacting in a much more childish way, and it's my rational side that usually keeps me from acting on those feelings.

I asked him if he thought I was pathetic or disgusting. He pointed out that I use those words about myself a lot, and that he doesn't think those things about me and thinks that I see myself in a distorted way.
He commented on me sitting on the floor facing away from him and I said that I couldn't stand the thought of seeing dawning realization and horror on his face as he read it. He said that wasn't what was there, what I would see was compassion. I joked that that was even worse.
I asked if what he read freaked him out. He said no, and that his graduate training had been pretty much all taught by psychodynamic and psychoanalytical people, so transference was something he was very familiar with.
I asked if I could now ask a question that was the childish part of me asking a stupid question. He said I could ask whatever I wanted. I asked "are you mad at me? do you hate me?" He said no and no. I asked "promise?" and he said yes.

I'm sure there are other details I'm forgetting. Honestly I just want to go to bed right now, but I wanted to type all of this out first because I will have forgotten even more details by tomorrow. It's probably a mess but I'm not going to go proofread and reformat now.

He didn't make me feel ashamed or judged at all. I felt like he really understood what I needed him to understand. He said he thought it was brave that I communicated with him about this and that he appreciated it. I didn't ask him to promise that he would never terminate me (because that would be an impossible promise to make), but I did get him to say he was sure that this wasn't going to be a reason he'd terminate.
I'd given a lot of thought to boundaries over the last 24-48 hours, and I knew that boundaries would make me feel safer and able to let go and trust, and so I'm really glad he seemed to get that and agree with that.
I was able to look him in the eyes when I got off the floor to leave at the end of the appointment.

Thank you everyone who gave words of encouragement, advice/feedback, and support. I really appreciate it.
I'm taking a deep sigh of relief. I couldn't have asked for it to go any better. I'm sure it's not going to be smooth sailing, but I feel like I really truly and deeply trust my therapist now, and it feels safe to do so.