Hi frizzcat. I'm glad you've already had lots of advice. My take on it is similar. You should get your second opinion, your Paed sounds awful. There is an increased risk for your DD, but that is all. And being a girl is also good news as it reduces that risk again. NT is neuro typical, 'normal' I suppose, but a nicer way of putting it. Two of my 3 DSs are NT, although DS3 is a bit quirky!
I spent all of DS3's babyhood worrying about him
but it was soon obvious that he was fine, lovely in fact, just a bit quirky as I said.
I think at a second opinion or appointment you should get yourself prepared with a list of questions about what to do next, about your DD etc. This time it won't be a horrible shock so you'll be in a better frame of mind to take things in and ask what you want to know.
It is a grieving process, you are grieving for the child your DS isn't going to be, so allow yourself time. It was 8 years ago that DS2 got his DX, but I can remember my feeling like it was yesterday. It hurts, but it does get better. What I usually say is that this DX hasn't changed your DS. He's still the lovely boy you described, it hasn't changed him at all.
I also found it best to concentrate on the next target, the next thing to be dealt with rather than looking far into the future. I only looked about a year ahead. But if it is any comfort, my DS2 was non verbal at 3.6 but has just passed his Y6 SATs and is off to MS secondary in Sept.
I also found that the other DC in his class were very tolerant and helpful once they had had a talk from the Advisory Teacher for Autism about invisible disabilities. It's not for everyone, but something to think about. The parents were generally nice, but not many playdates or parties here, either.
it is nice that there is another child, even if the mother is a bit OTT!
How old is your DS? The next thing is what support is he getting at school? Is he on school action plus, does he have an IEP, or does he have a statement. If not, perhaps you should consider requesting Statutory Assessment. This might be a discussion for another day, but come back and ask about it whenever you want.
You've found a great resource here, lots of people who have been along the same sort of journey, some at a very similar stage to yourself, some further along. I hope you find us helpful. 