Are you using a 1/16" endmill on 1/2" material? Most 1/16" endmills only have a cutting length of 1/4".
When using a 1/16" endmill on 1/4" material, I run at 70 ipm, 40 plunge and 0.03" DoC.
When I cut things like this, I would not tab any of the little circles on the outer band. I would just let the dust collection suck them out.
Part of the problem with the cut time is, if you are using a 1/16" endmill, you would be making 16 passes per cutout to get through 1/2" material. I would go with thinner material, or a larger endmill.
These usually take about an hour, and you can see, there are a significant number of small cutouts.