I am not a hairdresser but have been doing my own hair for years and use the same type of stuff and brand you do. If you want a darker blond that is not ashy or golden brassy look at the color called baby beige in the brown bottle, number 10 E. Sometimes I mix it with a lighter blond, also try using # 20 developer this will not lighten as much. Use the lighter shade for the highlights, but IMO highlights are hard to do on your own.
I have a problem though, I have kept my natural blond long into my 30's, now that I am older the sides of the hair over my ears has become transparent, I would describe the color as clear
. I use a bunch of grey magic drops and leave the color on that part for a longer time, but nothing seems to be happening. I will probably have to bite the bullet and go to a salon, I love the color on the rest of my head, just not around the ears