I wanted to check really quick have you in your scene Capture 2D actors reduced the Post Process BLend Weight to 0.0. It should be in the Details Panel all the way at the bottom under Post Process Volume. That significantly helped my FPS on the test level I am work in, mind you I am still setting right at 30 FPS. Let me know I am looking into the code is the shadows are removable or not.
Let me know if this works for you
Eric Ketchum