You can send your oil to Blackstone Labs for analysis. They will give you the amounts of different metals, fuel, coolant, etc. in the oil along with a brief analysis of the results.
There are at least three versions of the 4.0L MPI manual. The pdf that's been circulating for years with the missing page 59 is identical to the 1989 version except for the cover and the numbering of the Notes pages (up to 94 in the '89 version).
Have you removed the handle and cleaned/lubricated the button mechanism? I’m assuming the clips/rods/springs are all intact since you can futz and get it to work.
p.s. The obligatory “your grill is upside down” comment.