Your problem with the oil seepage at the ignition switch sounds like the (very common) issue whereby oil is entering the vacuum lock (shutoff) switch at the (electrical) ignition switch.

In short, this is a vacuum-controlled locking pin which - if non-functional - will eventually cause an inability to shut the engine off from the ignition switch. Most often, the culprit is the vacuum shutoff switch on the injector pump which, when it fails, will permit oil into the vacuum system itself. Not good.

(But you haven't reported a no-shutoff situation, have you?)

On the old cars, always run through the vac system rubber hoses, too. In my case, I had one vacuum port which was working, but marginal. This was sufficient to cause the no-shutoff condition.

Lou