Clearly there are a number of topics in the forum that discuss the normal things you'd have in a vehicle kit, those would be a great place to start. Doug has a list of specific recommendations somewhere on ETS.

In addition to those recommendations on supplies/kit... I think that since your vehicle is so key to your gameplan, you might want to review whether you've done everything you can to make it as capable as possible, some examples would be:
-Is it a 4WD van?
-Do you have at least all weather, or snow tires?
-Might even consider upgrading to ride flat tires, I expect that changing a tire would be more challenging for your particular situation, and if you get a flat bugging out in poor weather, or on back roads, you might be in a very difficult situation.
-Does the manufacturer have a second fuel tank option?
-Do you have a way to warm the interior, without the vehicle heater? Even candles will work.
-I agree that relying on 2 cell phones is a start, but, the other 2 comms, CB and FRS, are probably not very reliable. I have a ham license, so I always have at least a tri-band handheld FM ham radio and a pocket sized repeater frequency guide that covers the entire US. I've virtually never found a place that I couldn't hit an FM repeater on the 6M, 2m or 70cm bands. I have a mag mount tri-band antenna that I can connect to the handheld for better coverage.
-A use for the CB might be to actually install a PA speaker on your van, most CB's have the ability to drive a PA, and it might allow you to get attention, and communicate with folks trying to help you.
-If you can, have a secondary battery installed. Some vehicles have a place already set up for them, just need the battery and cables installed.
-In addition to normal lighting like a headlamp and flashlight, you might consider having something with significant throw, like a handheld spotlight to identify things around you, and signal.
-Are you able to move freely to the back of van from the drivers seat? If not, you need to think carefully about how to access your gear if you "bug in" to the van under poor weather conditions where you might have trouble getting in and out to get to supplies that you can't reach from the front. (Not sure how it's configured, you mentioned no lift.)

Ok, well those are a few thoughts. I did some thinking about this to help my brother a few years back, he has a C6 level injury. It's not easy to think through all of this, almost requires a field test to see if you have what you need.

You'll get great advice from this group.