3F is a finer granulation than 2F. 3F is supposed to to produce more pressure than 2F by volume (not sure about weight, but I would think equal volume of 3F weighs more than 2F).Therefore, if your gun is rated for a max load of 150 gr of 2F, a 150 gr load of 3F may exceed your max recommended load. More pressure should equal more velocity. No telling what will happen to accuracy, you'd need to shoot to know.

I can't answer your question about primers, but I have not heard that 209s cannot or should not be used with 3F, for what that's worth.