Hi ,
Most of the errors are saying that the mesh vertices are not skinned properly to the bones/joints. The final error indicates your model is entirely too small in Blender although it is only referring to one bone/joint. Here are some videos that show you how to properly set up your skeletal mesh in Blender and successfully export the result so that it can be imported into UE4:
Please view these and let us know if there is something that you need to know that they did not cover.
Thanks!