File blocking
is not a strong feature of FGTs. They only look the first extension. If you block only .exe it will not be blocked if it is inside a zip file. Also it does not use file signatures so if you rename a .mp3 to .txt it will pass..
In your case use some * and ? etc to reduce size
F.E.
Instead of blocking *.mp4, *.mp4, *.mpeg, *.mpg just block
*.mp* or even *.m* (to get also *.mov). That will save you some entries.
Personaly I block only exetubles .exe .bat .scr .com .pif and .vb* .cpl (.cpl are exetubles by the way) and big mutimedia files (.avi, .mp* .mov etc...)
PS. I agree it would be good to have
deny all unless permit but this is tricky for web (many sites would stop working)

and then you would need more than 55 file type to allow