I'm a glass half full kind of guy...have you driven it on the expressway for more than 30 min without the oil light coming on?
If the oil passages are clogged after running at highway speeds for a while the oil light will come on because the oil cant return to the sump fast enough to supply the oil pump with oil, so it runs dry and starves the engine of oil.
Pull over, shut it off for 15 min, let the oil drain back to the sump, start her back up and good to go for another 30 min or so.
It has to be highway speeds though, running around town at low RPM wont make this show up.

In my honest and humble opinion your first check of the oil level was a fluke, mine has done this to me on several occasions.
So now I just check the oil once a week, on flat ground, after she has sat all night (before the first start of the day) and I never get a false reading.

You can pull the valve covers pretty easy and have a look see, if the rockers are all covered in sludge then you can make your decision, if not, then just drive it.

If the engine were to grenade you can buy a good used one for a few hundred bucks.