Yep - oil in plug wells indicates failed camcover gaskets,ususally caused by blocked breathers.Looking at your pics,the breathers and throttle body havent seencarb cleaner for quite a while.That will be the cause of your troubles.Mayo in breather pipes,I would imagine same cause as mayo in oil filler neck - short journeys,particularily in this colder weather.GM 10/40 semi seems to be the best oil for keeping it to a minimum.A good motorway blast once in a while also helps clear the mayo.
Clean the breathers at least once a year (preferably twice imo) to ensure your new camcover gaskets dont go the same way as your old ones. And dont forget - only tighten the covers down to 8nm - which isnt very tight at all.

I find wynns carb/injector cleaner aerosol is best for cleaning the breathers etc. Looking at the state of yours,you will probably need 2 cans.

Nice write up youve done as you went along btw.Im sure some of those pics and accomanying script could be used for a maintenance guide of some sort.
