To get the center down you will do better with the 6" lap.
Typically the center of the mirror out to about the diameter of the lap, maybe just a little less will remain spherical. You might shorten the ROC in that area but it will be near no correction out to near the diameter of the lap.
So with your 10" lap it would be expected that you would not have much correction out to near the 5" mirror radius. That isn't what your measurements show but maybe you have worked with the smaller lap.
I think the best online reference for machine figuring is here
Two figuring methods are described, Zambuto's being one of them.
Note that figuring session are made of several steps of a few minutes each with changing offset (stroke distance from mirror center) by something like 1/4" or 1/2", usually while maintaining an overhang (portion of mirror diameter overhanging edge of mirror at the end of the stroke).
Zambuto's method corrects from outer zone first and working inward. As correction increases and correction is being added farther from the edge, overhang can become a negative number, meaning the lap's edge at the end of the stroke is some distance inward of the mirror's edge.
How many readings are you taking in your Foucault testing? You might take another set of readings to verify the last set. I'm not so sure the correction would have increased so much in the outer zone with a few minutes of work with 1" overhang.
If your readings are correct I think you will need to use the larger lap and work back toward a sphere to reduce correction near the edge. The overcorrection is likely to morph into a tde as you work that correction out and you would need to continue work to make the edge good.
When you learn to get the outer 2 zones good, the rest is easy... relatively speaking.
It's not likely you would be able to get those outer zone percentages to go down with the smaller laps. Maybe someone else knows how to do that without making an ugly edge.
Look at that link above.