The TS 55 can handle that depth of cut. Barely. Still, that's a deep cut, in hard wood. Definitely use the 12-tooth ripping blade. Squaring? Assuming you have at least a guide rail, rip a reference edge first, square one end, rip the parallel edge, and crosscut as needed. If you have an MFT, you can use the holes for the 90deg reference. For a board this wide, I usually just clamp a guide rail to the board directly with the help of a 12" square, which is why you need that first reference edge.