All that is good. Obviously, the smaller the aperture, the greater your depth of field (of depth of focus) will be. But you have another problem, and that is too much light. Either the lamp in your enlarger is oversized, or the thing was designed when slower papers were more common. You need to cut down on the light a lot so you can get at least 10 seconds at f/8 or so. That gives you some time for dodging and burning, and also lets you use an aperture where the lens is most likely to be at its best. First, make sure that the correct lamp is installed. Often, and mistakenly, a larger lamp has been fitted to the machine. This is not good on a couple of levels. First, it's too bright. Second, it can throw more heat than the machine is designed to handle. If the correct lamp is installed and you still have too much light, then get some neutral density gels from Rosco, cut them to size, and place them in the light path above the negative. I have an old Omega B600 that is just too bright, and that's how I solved the problem.