After an hour of EFCsearch in menu mode and another hour repeating EFC search in play mode I have the following working under the DVD device button:

Magnavox MDV-437 EFC codes under 0782
00036 Repeat
00037 Slow Motion
00054 Display Chapter
00058 Pause
00059 Mute
00100 #6
00101 Repeat chapter
00102 Title
00104 #9
00106 Stop/Menu
00116 Right arrow
00118 Power toggle---but I can't get it to set on the Power button
00119 Caption Language
00120 Next
00122 #3
00123 Stop
00124 Reverse play
00164 Step play mode
00182 Zoom toggle
00204 Fast Forward
00228 #4
00229 #5
00230 Root Menu
00231 #0
00232 #7
00233#8
00234 Root Menu
00235 Up arrow
00244 Left arrow
00245 Select/OK
00246 Open/Close ----but there's no button for this that I can see on RCRP05S
00247 Display/info
00248 Prev
00249 Down Arrow
00250 #1
00251 #2

This is miles ahead of where I got in 2 days of screwin' around, so thanks 1M!

If I were picky... I would sure like to find an "Exit" EFC, for when you get hung up in a menu or something. Exhaustive search mode was much easier/quicker/productive than code search!
But I wondered if the above pattern of EFC's infers a certain device that may provide a clue where the exit EFC code is.

Is it common for the power EFC to not go onto the power button? I do the
DEVICE-> hold Setup for 2 flashes-> 9-9-4 -> Setup -> 00118 -> Power
but the two confirming flashes don't occur the way that they did when I set the EFC to other buttons.

Oh well, its all good so far and the rest is gravy if I get it working so, THANKS!!!

Happy New Year, you've made mine start off well... and that's good karma, eh?