What kind of shape are the battery cables in? You can replace them with home made cables made out of 0 guage welding cable. This is very popular in the VW diesel crowd with notable increases in starter speeds.

With what you state on oil consumption, I would want to get a compression test done. Have a diesel shop do this since you don't have the tools. It's not an expensive test ($35 for the Datsun diesel pickup that I used to own).