many years ago I trained as fitter in the Army, no expense spared, we were taught, do a compression test will tell you if the pressure in the cylinder is low, put a small amount of fresh oil in and do it again, if the pressure increases its the rings, if not its the valves, simple, then check to see if the Valve stem seals are soft if they are hard / cracked, they will let oil in to the cylinder down the stem, if your burning oil it can only get in 2 ways from the bottom,or from the top

 

Either way, I think the op would need to spend alot to resolve all the issues his D2 has.
The labor cost would be very high, not to mention parts.
Considering he said it's an extra vehicle that doesn't get alot of use.
Of the many vehicles I've owned and worked on over the years, the D2 is by far the best...and the worst.
As it's easy to work on, but many of them break , and like dominos, and dollar you to death in the process.
In hindsight, I should have walked away from the one I bought, and looked at even more, lol
The op's is burning oil, and odds are, it's best to just keep it going for as long as possible, rather than fix it.
It is in need of major repairs, and lots of money.

I do think @ahab 's doing the pcv mod is a good idea too though.
Only a few bucks, and could help slow down the leaks.

 

if you want to go to the dark side......remove plugs , add and fill cyls with berryman chem dip 1gal can type. leave overnight. it will drain into the oil pan past rings etc. it does an excellent job on carbon removal and dissolves possibly freeing oil control rings. YOU MUST DRAIN OIL AND REPLACE FILTER BEFORE you crank engine. after oil and filter, spray 1/.2 can of brake cleaner into each cylinder, cover spark plug holes with a towel as itll blow crap everywhere and then spin engine over. Refit plugs go for a start then drive away. I did this on my 03 disco . it would always foul plug 7 with oil. it stopped the miss and for me it worked.