Oh, well done for going to therapy Mosp! You will start getting better, you know :) And you're worth the care you give yourself ... so make sure you care well for yourself.
I think I understand what you're getting at. Firstly, you really need to remember that your penfriend is lonely & bored - his penfriends are probably his only line to the world outside, they mean a lot to him and he's very likely to read more into his letters than the writer often intended. Secondly, although he must have loads of lovely qualities - and you quite rightly give him solace by appreciating his good side - he is a far from perfect human being. He has some bad flaws. His penfriends have a responsibility to remember that.
Please contact your co-ordinator for support.
The other part is your feelings about what he said re your references to sexual things sometimes in your letters. There's a possibility he may be making this up: reading something into perfectly ordinary remarks of yours (you know, like the twerp in the pub who says "The lady wants a large one, haha" 
)
From the little I've gleaned from your posts, it also seems possible you did do this sometimes. I went through quite a long phase of being a little too sexy - inappropriately - because, to cut a long story short, I had the idea it was the only interesting thing about me. If you're a bit like this, it's a vulnerability and will be something to incorporate in your counselling.
What's interesting about this is the reflection of what happened with C. Both these men responded inappropriately to a vulnerability (real or imagined) in you. Nice people don't take advantage of such things. They quietly change the subject, take a step back. Nice people don't try to interfere with another person's weak spots. Both of these guys, in different ways, did try to take advantage.
Please don't beat yourself up about having vulnerabilities that could be exploited. You're doing the right thing for yourself by doing therapy. Please notice that everybody has vulnerabilities! There's nothing wrong with having some. Good counsellors can teach you how to respect yours, and to protect yourself with fair boundaries.
What Bertie said about a freeze response is very true. When we feel threatened in some way, by far the most normal reaction is "rabbit in the headlights". It's actually the safest response in most cases. Some people, sometimes, go "rabbit" when it would be more helpful to assert their boundaries. You will learn how to do this in counselling.
It's all good, Mosp :) Good therapy does leave you feeling somewhat flattened! If it didn't make your mind do some work, it wouldn't be doing anything would it?
All the best. Hope you sleep well.