Hello Edward,
I'm glad you were able to get it running and yo ulike it.

Of course it is not as fast as the original NTVDM on x86 due to the lack of V86 mode in x64, but better than nothing. I even got DOS Games running in window (which iirc. was not possible with the original NTVDM, as this one always tried to go to full screen and direct VGA for better performance).
Are the strange error messages produced by the NTVDM or by the DOS application running in it?
It tried to run WordPerfect 6.2 for DOS and it started without a problem in your VM... Interesting.