What you try to do is against admob banner guidelines.
"banner ads should not move as a user scrolls, as users may try to click on the menu but end up clicking on the ad accidentally instead."
I must admit that it is confusing when you compare it with native ads which are banners that are allowed to be place in scrollable content.
Personally I would just make my content fit in a panel of 100%y - (banner.height+smallgap) and let the banner refresh every 60 seconds or so.