Some clarifications:
1. There is no assumption of normality of response variables from a DOE nor is there an assumption of normality to use ANOVA. In fact, ANOVA is fairly robust to distributional abnormalities. The assumption for quantitative analysis is Normally and Independently distributed residuals with a mean of 0 and a constant variance (NID(o,variance)).
2. Residual plots are quite useful for identifying model issues. The Prediction Profiler is what you are looking for for main effects plots. If residuals are quite different around one level than another, this can indicate the factor has an effect.
3. You must make sure there are interactions in your model to get interaction plots (Stage 2).
"All models are wrong, some are useful" G.E.P. Box