Piston ring wear is usually the cause of high speed ( RE high load ) oil consumption. Connecting bearing wear also increases oil consumption because there is more oil being thrown onto the cylinder walls.

Making a list of car people along the way will be helpful in case of a breakdown. They don't even need to be Mercedes people, old car clubs, people on a car message board such as Hemmings would work out.

Making this run with coverage from a car magazine / U Tube channel might be helpful as well if you are looking for backing along the way.

If you are looking to do a 1950's style excursion with minimal electronic help that would be OK too but be sure to take a cell phone that will work in Canada in case of dire emergency.

Bring tools that will fix an on the side of the road breakdown. Don't bring tools to change a major breakdown such as a ring and pinion / rear wheel bearing as you will need to seek the assistance of a shop anyway.

Try not to brings things that are readily available along the way as you want to reduce weight. I'd use auto parts sites to see what parts can be purchased along the way then adjust the spare list as needed.
If the tires are more than 5 years old I'd consider replacing them. If they are showing any signs of cracking, replace them. I'm guessing you have 14" tires, these can be difficult to source along the way. As a dire emergency on the road, you could use a 14" trailer tire.

You might consider using a taller tire to reduce on highway revs but be aware that this will load the engine harder and increase oil consumption.
I'd bring 2 fuel filters, buy an oil filter when needed and only 1 gal of oil. Fuel filters are critical to vehicle operation, you can skip an oil filter change if you can't find one, buy another gal of oil when you have a qt or two left.
Small , light, OK to bring
OK to bring, probably difficult to source along the way.
I'd bring car water in 1 gal antifreeze jugs as this is easy to store and a leak in one won't result in the loss of all.
What has been changed in the past year or two? 2006 is back far enough that they might need to be changed again.

I'd be changing all coolant hoses, thermostat and bypassing / plugging the heater core. This eliminates a leak point, reduces AC load and reduces in car temps dramatically. I add a heater valve to all cars under my care and is the next best thing to AC.

Repack the front bearings
How many miles on this?
How many miles on this? At minimum I'd bring along a spare belt that runs the alternator and water pump.

How many miles / starts on the starter / battery?
I wonder if using car club / message board contacts would stir up a ride along for x miles person. They would fly to your current location along the way, you would drive towards their home, drop them off then continue on.