I'm trying to find a flat dark blue in a can but all I could find is light blue. Satin sheen seams to turn out blotchy at least for me and almost all blue paint is gloss. Your paint job turned out great!
Back when I mixed R-M and Dupont paints,you could add a flattening agent to the mix to kill the gloss--many guys wanted that flat black like dark gray primer look for rat rods,but the primer didn't keep water from penetrating and eventually let it lose adhesion..
I mixed many gallons of black with the flattening agent and it came out looking like the dark gray primer,but repelled water and wouldn't start lifting after a few months..
I have read cornstarch works as a flattening agent too,never tried it myself..stuff I used at work was a thick liquid that looked like cream of wheat only translucent..