Being that it is Testors acrylic (which usually comes out satin to matt regardless of color), and spraying at 45psi, just the high pressure would be enough to partially dry the paint before it hits the kit, giving you the rough textured finish.
I haven't used the Testors acrylic stuff much, but what I did use, was pretty thin to start with and didn't need much thinning to airbrush.
Your thinning ratio is probably good, but your airpressure is way too high. 20psi would probably be more than enough to paint, lower when you are doing the final "wet" coat.