The chart looks pretty good to me. You shouldn't have to increase time much, if at all. Once you do a test strip (I almost always start on a grade 2) and you see that your blacks hit a rich black, that will likely be your time. After that you will just be adjusting for contrast for mid-tones and highlights. This is generally speaking though. If you test at grade 2, but it's actually a grade 5, keeping that same time but raising the contrast can suffocate shadow detail and you might have to lower the time a bit. So, you may have to adjust your time as you increase or decrease time to control density of shadows and highlights more accurately, but it won't be far off.

It really depends on your workflow. I like to develop for higher contrast so that I can squeeze out 20x24 prints of any 35mm negative a I choose and never really print smaller than 11x14. So, at 11x14, I test at #2 and it's generally not far off...16x20 I test at #3, 20x24 at #4....I'm usually pretty close so my times don't vary much, if at all, when I use a colour head.