I'm the brother who owns this '87 bronco ii.
I wanted to thank everyone for their input and give an update.
I have driven the vehicle a few hundred miles and a few 'trips' more than five miles just around town. I don't notice any leak under the vehicle after warm-up and driving a few miles as I did prior to my brother tightening the valve cover and oil pan bolts. I also don't notice any drop in the oil level on the dipstick. So I can only assume the leak came from either the valve cover or oil pan and it was getting on the oil filter somehow - my best guess would be the valve cover. It still smells sometimes after it warms up but much less than it used to. Hopefully the smell will go 'away' as more of the oil is burned off.