Wow. Quite a long post and comments. Wonderful!
The core issue is acceptance and understanding. No logical argument can be applied to this. A person just needs to accept a person who is transgender and then seek understanding. That is where things become difficult. If you don't know who you are or where you are going and leave things open ended, a spouse will feel off-balance such that they do not know what to expect or know who you are as person. They will build walls because of lack of emotional trust. What has helped me, is that I always try to determine something concrete, what I know about myself that I can clearly communicate. And for all of the stuff that I don't know, that we will figure it out together.
One thing that I have been very clear about these last six months is the following: either I need to figure out ways to cope or I will have to transition.
Now, I consider myself, generally a very self-aware person. What I did not realize, but do now is that the anxiety which envelopes you when you can no longer cope is overwhelming. I just went through 3 weeks of hell. It is like getting thrown into the fire. I always thought that my decision to transition would come after careful evaluation and contemplation. It can happen that way, but ultimately the alternative happened in my case. At that point, you just give in. You have no choice.
For many of us here who are contemplating transition, just be aware that this can happen. And let your spouses or SO's know that as well. So, that they can face this with you, with their eyes wide open knowing the worst possible outcome. They need to know how serious this really is! I've been through the ringer my entire life, but I had no idea that I would essentially have high anxiety and high blood pressure for 3 weeks. It could have killed me. I almost blacked out driving my car, etc. Bad stuff.
Anyways, Emma be brave. I didn't mean to scare you and I hope I helped. It scared me, so I feel scared for everyone else.