Re: #2, "The kids are 20?": I found a Twitter conversation showrunner Rafe Judkins had with fans in October 2021 after the first stills of the show were published in Entertainment Weekly. Rafe tweeted:

We aged up the Emond's Field Five from the books because sometimes TV shows with a bunch of 17 year olds as leads feel more like YA and Wheel of Time isn't YA

This confirms my interpretation of how the characters— at least Rand, Mat, and Perrin— were portrayed in the books.