you can use any two colors you want on the text. just choose a darker text color, and use a midtone to aa to the light bg.
the color used for aa on the text isn't helping. try a different grey or blue that has a value between the two colors you're using. bottom half in general doesn't seem up to par with the top half of the image.
no.
but you could use the light green as the AA color, and the dark green for text. the aa is only present on 'quest' though, on the rest of the text it's just banding that isn't helping no matter what color it is.