The oil youre using is a bit thin- is it Diesel rated? I used to use synthetic in cold seasons with my '79.

Ive recently come to the conclusion that its critical to seal the engine envelope..valve cove gasket, oil pan, the oring on the dipstick, front and rear mains, breather grommet, oil cap, etc. If the engine isnt sealed, you can be drawing huge volumes of oily air through the crankcase.

The plugs may not be the problem-with this sort of oil consumption, your compression could be low. What I would suggest is to do three consecutive glow cycles before attempting ti crank. And get some of these problems looked at when youu can.