Can I use USB for most control surfaces?
For example BCF2000, MCU, Faderport, X32, and others that i dont know about?
I want to know cuz i  notice on BCF theres MIDI in out...and if I do need to use MIDI then my interface is a problem cuz theres no free inputs
 
Also when I want to use a keyboard (PSRE223) do i have to plug  both IN & Out on my interface? I understnad that obviously MIDI IN means signal from Keyboard>Intfc meaning controling the DAW but whats Out....? Does it make sounds on my keyboard or soemthing lol

First if you are already using your MIDI input for a keyboard controller, then you are best to purchase a control surface that uses USB. Then you will not have to swap the cables. I made a simple switch for the swapping but I no longer need it as we find most new MIDI gear uses USB connection in place of MIDI a connection. 
Some devices feature both midi and USB connectivity.  Both will do the same thing. 

If you don't plan on using the sounds within the PSRE223 then there is no need to use MIDI output from the interface. The sounds within Sonar are way better so no point wasting another $2 on a second cable.