First, I'll address your fears:
1. That's a possibility. I'm afraid you'll find that there are many different therapists and therapies for a reason... there's no one size fits all, and not working with a particular therapist doesn't mean that there's something wrong, necessarily. I have consulted with a number of therapists, and have had to change therapists before. It's not easy, but it's also not a bad sign. Most of us hate changing therapists, but not liking it doesn't make it impossible, or not worth the effort. It is absolutely worth the effort.
2. Is there a reason to believe you could not go back? I left one therapist that wasn't working for me, saw another for a bit to try and sort things out, then managed to patch things over with the first one. It's been over a year since then. Even if your current therapist says he would prefer to make a clean break, this does not mean there is no other therapist that will work. It's a morbid thought, but your current T could be hit by a car tomorrow morning, and then you would *have* to find another T. Sadly, some of us have been in scenarios where we're forced to find new Ts. You would be able to do it, too. And if you leave CBT, but find you don't like psychodynamic (although if I were you, I'd give it a good year before deciding you don't like it), you can find a new CBT therapist. They will not disappear from the planet just because you leave this one T. I'm not saying that to be mean or condescending -- I'm trying to point out how your fear is causing you to think very, very narrowly.
3. This completely makes sense. For me, it is the hardest part of talking to a new therapist/pdoc. It's like the end of any relationship. It's sad, it's hard, and it doesn't seem like any other relationship will be the same. But a relationship doesn't have to be the same to be equally good. Still, opening up is tough and I sympathize -- but do you feel you are REALLY opening up with this current T?
4. Do you feel your current T understands you? If not, what do you have to lose by looking for someone who does? You may also find that no one is ever going to *fully* understand you, but a good T will help you populate your life with people who understand various bits and pieces. My H knows me better than just about anyone, but there are things about me he doesn't understand, and vice versa. My T also understands me extremely well, but it's the same. There are things he doesn't quite get. However, he has been better and better at helping me identify people in my life, or ways to find people in my life, that might be able to understand better than him.
5. Probably the same as above. It's unlikely any one person can fully help you. But, even if you were to believe that it's possible that no one in the world could help you... you might as well try to see whether that's actually true. I'm appealing to the scientist in you
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I will continue to appeal to the scientist in you by asking, how would the world look if the great biomedical scientists of the world didn't try something because it might not work? How would we ever make any advances? Now, it's very hard to look at one's own mental health as a science problem, but in a way, it is... the methods for addressing the problem are not as defined, and cannot be as rigorous, but still, it is an issue of your health. I think we tend to get wrapped up in blaming ourselves for our issues, or feeling like we are the one person in the world beyond help, while everyone else deserves assistance. Not true. Treat your health the way you would any subject in a clinical trial you were working on. You deserve that level of scrutiny and tenacity.
Second, because this is really long I'll just come back and answer your actual questions later. But I'd like to turn your fears around a little into other questions:
1. What if there are several therapists out there who might work well with you, and you never meet them because you talk yourself out of it?
2. What if giving up CBT and this therapist are exactly what you need, and you stay stuck in the same place because you hang onto something that isn't working for you?
3. This is a tough one, but I would say, what if all the emotionally difficulty of opening up to someone new was able to show you that although your relationship with current T is not a bad one, it wasn't the right one at this time in your life?
4 & 5. What if you miss out on the understanding and help that others are able to offer because you close yourself off to the possibility?
I'll get back to your questions a little later, but I wanted to assure you: you CAN do this. Don't let your fears corner you into black and white thinking. Your past experiences are not your destiny. Things will hurt and will go wrong sometimes, but there is support out there for you. I mean, you've gotten a fair amount of support from this forum, yes? And I'm sure sometimes this forum has hurt you. Both those things have happened to me. Isn't the support you found worth the risk?