How to adb chmod 750 on /sdcard using batch
This generally won't work. Android sdcard volume is normally mounted with "-noexec" flag to prevent exactly what you want to do from happening, no matter what FS type (vfat or ext2/3/4) it is.
Since you have a rooted device, you may want to try remount sdcard volume without noexec flag - not sure if it work with FUSE filesystem drivers, though…
I know I'm almost a year late to the party, but try using:
adb shell su -c chmod 750 /sdcard/path/to/dir/*The little wildcard at the end will apply the permissions to every file in the folder.
You could also use something like:
adb shell su -c chmod 750 /sdcard/path/to/dir/*.apk...to only apply the permissions to APK files in the directory.