Your exactly reproducing the wrong gate drive circuit from your previous post . As only difference, you're using a EL7457 now.
If you would have mentioned, that you're going to design a buck converter in the previous EL7457 related post, I'd already told you to use a level shifting driver instead. I suggest to go back to the previous thread and figure out, why the second version worked, but the first didn't.
It just wanted to point to the problem, that a floating (or [/i]high side) gate drive is required with a buck converter, not suggest a particular solution.