Does your world have a twenty-something degree axial tilt like Earth? If so, your intertropical convergence zone is going to shift northwards in the northern summer, and southwards in the northern winter. The shift will be rather more over land, and less over water. A straightforward reference is http://www.physicalgeography.net/fundamentals/7p.html.

I can't tell the order you've followed, but it makes the most sense to figure generalized seasonal pressures, then generalized seasonal prevailing winds, and only then generalized ocean currents. A whole lot of the driving force for surface currents comes from winds.