I think you need more Strength. My level 33 FS has similar Strength and Tackling stats to yours. Last game I had 6 (!) missed tackles. All of them were against running backs. From the replays it looks like my FS was just overpowered by them. I'm looking at increasing his Strength in the future to help stop the missed tackles against high strength running backs. When FS's miss tackles it can frequently cost the team 6 points. 
Olaf the Stout
Olaf the Stout
