Things started well but now .19 FPS and slowing

[Selur]

I chose that to match the framerate supposedly of the source. I'm open to becoming educated on what I am misunderstanding.

You should read up about telecine and ivtc and check whether your source is telecined or even soft telecined.
In case it's not telecined, but really interlaced (which is rather uncommon for DVDs), sticking with 2*29.97 would be what one would prefer to go for, to keep most of the motion information.

I do notice that all encodes at start ramp up to a high frame rate (over 200) then framerate steadily declines over the length of the encode.

yep, that sounds 'okay', when complex filter scripts like qtgmc are used.

P.S. I did get a compile error for ffmpeg when compiling the vapoursynth addons and had to comment out a line that was no longer supported.

Line # 98 in build-and-install-vapoursynth.sh
--enable-avresample

Haven't used that script for ages, I usually use:
1st build-vapoursynth.sh
2nd build-plugins.sh
=> I'll try to look at it in the next few days.

Cu Selur

Cu Selur