1) DYS does not require IQ testing anymore. Talent search tests (which are much cheaper) can be used. If DD10 qualifies, joining DYS would be very helpful because your family consultant can help with resources. Some free resources that might be helpful are here: https://www.davidsongifted.org/Young-Scholars/Free-Guidebooks

I can’t help with the rest of your questions, but you might want to search the archive.