Those are some great plots! The strain plots are interesting. They show some hot spots. Maybe some gusseting makes sense in some of these locations? Might be worth an experiment to see what displacement improvements you get by chasing strain hot spots. You will get a feel of whether it is worthwhile in a couple of tries.
Also, are you including your tool deflection in your stiffness figures? It seems like you are hobbling yourself including tool deflection - your tool is dictated by the process, not the machine (within limits), so why include it in machine design decisions? If your tool is contributing significant deflection, you might consider discounting it...