@littlefish, you are so sweet to be so focused on understanding how you can support your SO, and respecting his wishes.
If I knew 15 years ago that my SO wouldn't be coming out until a couple weeks ago, I'd probably feel overwhelmed by the prospect of keeping a secret for so long. I'm sure that I was only able to keep it by focusing on one day at a time. Now that my SO is coming out and pursuing feminization, I am delighted to be sharing my experience each day here in this SO forum
https://www.susans.org/forums/index.php/topic,241591.0.html. I just can't contain my enthusiasm, and want to celebrate each step with people who understand. I also want to pave the way for her as she gets used to the idea of conversing in a forum. I know that many people here will appreciate her story, understand what she's been through, and embrace her with hugs of life-giving support.
Regarding your questions about my SO's coming out, it is happening so suddenly that I'm afraid to ask what her plans are.
I knew that she was repeatedly rewriting a letter to our dr asking for a referral for hrt, but when she had second thoughts, I felt so disappointed and heartbroken, I had to lock my mouth to wait patiently for her to deal with her fears. I felt relieved when she handed the letter over during her annual physical a week and a half ago.
Similarly, she told me today that she might be ready to come out to my daughters (adults) the next time she sees them. That would make me so happy as I firmly expect them to respond with respect, curiosity, and some understanding.
Likewise, she is considering leaving her nail polish on for each of our 3 or 4 appointments this week. I'll take on my mother bear role of protecting her from any offensive remarks, if needed, but this has to be about her, not meeting my needs or expectations. I must control my need for her to come out. I must follow her lead so she feels safe and grounded.
You asked when is the best time to come out. I think that the best time is when the person feels safe and grounded, or otherwise ready. I understand that transitioning happens when a person feels ready for the consequences. Coming out might be the same. Please help me understand why your SO is wary of people knowing his plans. What responses are he expecting? If any of their responses are unpleasant, what do you want to do? What responses would he rather have? How can he get the responses he wants?
I can only imagine that if he is afraid of being intimidated by his family, then coming out might feel more right when he can ask for forgiveness instead of now when they might try to withhold their permission. Is that what's going on?
On the other hand, she might be waiting for the opportunity to make a Grand Entrance as Her Real Self when the transformation is completed?
Or maybe she just wants to put all of her energy into transitioning, get it over with, and then deal with the consequences?
Have you considered consulting a conservative Christian pastor to help prepare you to respond to your family members?
I think that my SO is coming out now because the fear isn't so suffocating. We identified the tiniest baby steps, and then built on them. Each interaction is showing her that she can build a safe world around her, especially within my support and perspective. I'm delighted to be making such a valuable contribution to such a valuable life.
I hope you are finding the support here that you need as you remain in the wake of your SO's journey.