Hi Robin, as Chrissy said I also suggest taking it a step at a time. If you're going slow you already know this. Don't worry too much about all the things in your future, just face them as they come up.
For your father's family, can you find somebody who is more likely to be accepting? If you can, try to make an ally of them. They can then help you as you come out to more people. I found an unexpected ally like that in my own extended family and she has really gone to bat on my behalf when a transphobe in the family jumped on me.
I'd suggest sooner than later. You may find more support than you fear. And if not, might as well rip the bandaid off and get it over with. Odds are that people will come around over time as they think about it and as they realize you aren't changing.
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