I took Geofd’s advice, and purchased the repair kit. The washer that sits in the nut was not behaving. The nut would barely reach the threads of the valve, and upon tightening, would pop off. I was able to get it on eventually, but water just poured out ridiculously, mocking me.
So I went out and bought a SharkBite shutoff valve (forgive me). After cutting off the old valve, I discovered the SharkBite was too small to fit, barely. Someone soldered a slightly wider copper pipe to the original copper pipe. I cut the pipe back to the original, and successfully attached the valve. Now I understand the difference between outside and inside diameter.
I do not like touching plumbing. It seems no matter what I do, water likes to find its way out to laugh in my face. Whatever I did wrong with the replacement kit, I thank you, Geofd, for your good intentions which sent me down the path I ended up in I don’t know what I did wrong with the repair kit. I replaced the bathroom vanity and sink yesterday, which went surprisingly well. I spent all day today trying to fix the smallest leak. I’m exhausted, but victorious.
I know you guys would know exactly what to do in this situation, and I can understand whatever criticism you’re thinking. I’m just glad I was able to solve the problem and stop the leak. Thanks to both of you who took the time to reply, it means a lot to me.