Well, it would be great if you will post which 14-18 functions that are missing. Have you actually tried using 10047 for the TV, 20522 for DVD, and 20060 for VCR functions? Do that and then post which functions are missing. For example, using 20522, I expect that you will be able to bring up the DVD menu and the arrow and transport buttons should work, but I'd like to find out for sure.

Of course, I've tried to get you to just install RMIR and load some RCA upgrades, because then you can read the function names and find the one that are most likely to correspond to the missing ones. It's a lot easier than me guessing which function name matches whatever you're missing. However, I'll probably have to help verify the correct EFC for a given function--the EFCs vary depending on the setup code in use during assignment.  That mostly depends in whether you want to try to putmost functions on one device button, or if you would prefer 3 different device  buttons for operating the TV, VCR, and DVD.  The latter approach is simpler to set up.

Once you have some candidate EFCs, test them by tapping P (Setup), and then entering the 5 digit EFC, holding down the 5th digit for a little bit. The remote will send the corresponding signal. For example, if you're using 20522, tap P, then enter 00016. Maybe that will open/close the DVD tray. (I got that from this upgrade.  Or try 00227/00219 to provide discrete On/Off.  That works with standalone DVD players, but I don't know if it will work with the combo unit.  If not, try it with 10047.  That will send the same function number, but device 15 instead of device 5.  Or perhaps both will work.

In post#9, I gave the link to the 9XX Command instructions, but here is the simple version.
After having assigned the appropriate Setup Code,
1) Press P until 2 blinks
2) Enter 994  (2 blinks)
3) Tap P
4) Enter e.g. 00227
5) Tap  e.g. PIP
The remote should blink twice. 
Now if the unit is off, it should turn on,  If it is already on , it should stay on.