It’s very important to apply scale in Blender before you export anything. If you select your armature/mesh in Blender and look at the “N” sidebar there should be 1.0 in all those “Scale” entries. In Blender I’m using scene settings metric with unit scale 0.01. In the “Export FBX” settings (like shown in your screenshot) I’m even using 1.0 as scale … but I switched to Y Forward Z up after verifying my skeleton in some MS 3d viewer. I think that Y Forward thingy does not matter in UE4 finally - and it would not fix any of your issues (I’m sure that Blender does not support the native UE4 axis like Maya anyway (which is not that much of an issue as UE4 got a very good retargetting tool)).