if he cashes his paycheck, knows how much he owes you, but does not GIVE you that full amount....either he bombed remedial math or it IS deliberate. I think you stated your point of view just fine..and I think his reaction is a bit telling. nothing to do but wait til next Friday and see what he does!
good luck with the freelancing! i'm "supposed" to be working an article right now, but I keep stalling. grrr.