I was able to fix the problem by disabling VT-d in my BIOS. As it stands, Windows 10 1803 will not boot if this is enabled.
Seth_N_Michel Thank you for this amazing contribution. The time you took and the skills and experience you applied to come up with this amazing, simple and easy to do solution has just saved me $2000 for a new computer I didn't need. My ASUS P6TD Deluxe has been a "just-right" companion and now we can truck on without fear that our Windows 10 operating system would not become unsupportable. I turned on computer/tapped Delete key/searched in BIOS relative to processor/CHIPSET/found VT-d. The VT-d was ENABLED so changed to DISABLED and voila! Installation completed successfully as did the catch up updates. Thanks again to all for this great site and the help it gives through the generosity of the many contributors. E pluribus unum