When the oil light comes on that indicates you have little to zero oil pressure and the oil is no longer circulating around the motor. At this point you need to stop running the motor ASAP. According to your post you drove another 10 miles at 65 mph after the light came on. If this is true you are very lucky to have a running motor now in your car. If this should ever happen again don’t worry about finding a parking lot, pull off the road and turn off the motor and call for a tow.
At this point your choices are keep the car. It seems to be running OK. Are you adding oil between oil changes? How much and how often?
If you are burning oil and hearing a lot of noise from the motor “grungier” as you call it then you should sell the car or trade it in for another one, BEFORE your motor deteriorates further. Fixing the motor in the car means a complete overhaul, or a new block and without an insurance company paying for this work it is too expensive for you to tackle.
The oil change place is responsible for this whole problem. The either stripped out the threads in the oil pan and didn’t realize it. Or, they knew they screwed it up and put in a drain plug designed to fix stripped out holes and that didn’t work. Since the drain plug itself is gone you’ll not know what kind of error they made but if you oil plug is gone 1,000 miles post oil change they definately messed it up. You should have had their insurance company pay for proper evaluation and repairs if needed of your motor at that time. 10K miles and months later you can’t do that now.