I’m just a rookie at this, but I have had some success in my first few attempts at cutting aluminum. Maybe someone with a bit more experience can chime in if I’m not right in my assumptions. Your settings look the same as I have used and I used the same type bit. My RPM were roughly 13,000 RPM, about half the speed you used. I would suggest slow your RPMs down. You should be getting chips, or little curls of aluminum coming off the bit if your speed right. It almost looks like your melting the aluminum.
On the outside cuts, I have manually slowed down the feed rate with the slider in Repetier if it looked like it needed it. I also have an adjustable speed control that my router plugs into, so it’s easy to tweak the RPM while it’s cutting.
Have you tried the trochoidal settings in Estlcam? To find them, you need to turn them on in the Tool List window under View.