First, please stop shouting. Typing in all capital letters is considered 'shouting,' and makes the post harder to read.
Second .. the barn will NOT have a main panel. The "main panel" is at the meter, where you have that 70 amp fused disconnect. That's where you bond the ground wire and the neutral. So, yes, you get to pull four wires.
Keep the ground and neutral separate at the panel in the barn. Run a wire from the ground bus to the ground rod / ufer, whatever. This is the GEC.