Are there other mechanics you can use from now on? It is experiences like this that convince me to work on my own car--that and mechanics require payment. How dare they?!
I found out to spray silicone into the hole from this video:
Then he said to use this machinist's pick to pull out the boot:
https://www.amazon.com/gp/product/B0...d4606f7902f458
I did not want to wait for shipping, so I went to Harbor Freight, where I found a similar set of four picks for $4. None of them were the right size. I heated a straight one on the stove and bent it 90°, but when it seemed like I had the pick all of the way in, I could not catch any edges to pry the boot loose. When I used needlenose priers it broke off a chunk. I ended up using a big screwdriver to break it into chunks and then removed that with a "combat" flashlight and a pick.
I finally removed all of the hard plastic, but could not seat the spark plug puller. There was a ring of charred rubber (silicone?), which took quite a while to extract, but I made sure to spray the hole with compressed air until nothing came out and dried out all of the lubricant that I could.
Zero PSI. In fact, I tested the remaining two cylinders and according to my compression tester all cylinders put out 0 PSI, but when I clamped the gauge and watched it from the driver's seat, each hit about 60 PSI.
I am going to rent one from Autozone and try to figure out which component is bad, but I doubt I will have any luck exchanging it.
Lifetime warranty...