If my wife dies is there any way to marry again or is that it?
I think that's it, but I'm not 100% sure.
I see my "child" on the dynasty screen - but is there an actual unit for my new child? If so I cannot find her.
Your children will appear in your capitol city when they reach 20 years old.
Is there any way to outright buy a unit if I have the gildar? Speed produce one?
No.