Eliminate your 4x4s. Run a double rim joist and use hangers to attach your stringers to. The double band joist will also give you a secure piece of framing to attach your posts to with lags or through bolts. Don't notch them, it weakens them. Make your self a water level if you don't have a laser level. Buy enough clear plastic hosing for the project and fill it with colored water. Add a teaspoon of dishsoap to help it flow. You can use it to level all your concrete footings so they are perfect. If you mess up, just cut a few pressure treated shims to level it.