i manged to reduce it by 1KB!!! by running cleanup and i get rid of extra hidden Geometry

And i agree completely with you there is nothing more to do all my search result end up with the 3 steps above + this new one to optimize the mesh. there is another way to link the objects to each others " this helpfull in duplicated objects" but this wont help in my case
because i am looking to reduce Fbx not MA

i have no idea about the extra load in the file before Thanx for teaching me this information.