That is a nice looking build!
Strange about stopping when you turned on the vacuum. You know how lights dim when you turn one on? Maybe combined with the dw660 it pulled too much power and the controller lost power long enough to stop the cut.
Facing the entire board with a 1/8th bit seems like a lot of work on the bit especially without any sort of cooling.
Side note: did you buy the electronics/hardware kit or did you buy everything separate? If the first, where did you find the conduit lengths to use the belt included in the kit? How big is your actual work area?