Pressure difference is the only thing speeding wind up. The quicker pressure changes from spot to spot, the higher wind speed is. All the other forces, such as friction, only reduce wind speed and/or change its direction.
Wind would be perpendicular to the isobar if the Earth wasn't spherical and rotating around its axis. But instead all moving objects, including wind, are subject to the influence of the so called Coriolis force.
It deflects wind from the normal line to a certain angle. In the Northern Hemisphere air is rotated clockwise (to the right) and in the Southern - counterclockwise (to the left) with reference to the movement direction.
The friction between air and sea is lower, that's why it's deflected more there. The angle is usually 40-50° above land and can reach 70-80° above sea - then the wind blows practically along the isobar.