re: 5-6000 miles with no oil cap? Dipstick gritty, how worried should I be?

My field of expertise is Diesel engines in heavy earth moving equipment and not gas burning automobile engines.

But having made that disclaimer, I’d say you’re at significant risk of a major engine failure due to contaminated oil. That grit you’re seeing on the dipstick is only a small sample of the dirt that’s inside your engine. You need to go get your car checked out by a professional.

ETA: If possible, see if they can take a sample of your oil. Things to look for will be elevated silicone, water, and aluminum.

Im sure the silicone Levels will be high due to the ingestion of a lot of dirt. There will probably be trace water as well. The real concern would be high levels of aluminum or other wear metals. If those are present, you’ve already got bearing damage.