My name is Jackie and I started transitioning when I was 64. Like you I have been married a long time.
Firstly be careful with the herbs as they are stronger than you may realise. You should find a specialist (endocrinologist) to help you. I am sure one of the US members will advise you on that.
Initially my wife was understanding about it. I tried to take things slowly and bring her along with me but it became more difficult for her. We separated for a while but we got back together again. The process she went through was akin to grieving and eventually she was able to accept me as female. As you know as a marriage matures companionship and love become far more important than the physical side. Now we are back together my wife is my biggest advocate.
I wish you all the best on your journey and hope that your marriage survives (lots do) but please get medical advise and monitoring soon.
Best regards, Jackie