information on how long the remarketer code/cookie lasts
The length of the cookie is under the control of the advertiser.
What I am reading here is that if somebody clicks on a "remarketer's" ad then visits my site, then Google will display ads on the remarketer's Adsense account not on mine.
This is not accurate.
AdSense publishers get paid the same as always when a user clicks an ad on one of their pages.
The new thing here is that the advertiser has a new tool for targeting the user. As always, the more skillfully the advertiser uses their tools, the more productive the ads will be, which is win-win for both advertiser and publisher.