Most of the England WC boys have struggled. Take out Sterling and there aren't many success stories. I'd suspect he hasn't been 400% all season. I'd expect an upturn in form next season.
Perhaps, but even recognising his poor form this season, even if you look at what his normal/average level is then he's still one of the weakest, if not the weakest, play in our starting 11. He's also not going to improve given his age and his value will start to decline soon. Everything points to selling him this summer and getting in a replacement