Well, I have an update. After 48 hours of soaking and icthamol wrap over entire foot, I got a call from barn manager yesterday saying "he is three legged lame" He could barely walk out of his stall. I called the vet and she said to get there, soak the foot, and inspect along the coronary band carefully. She said call her if any swelling at all above the foot.
I got there and did exactly as she said. After a 30 minute soak, I asked him to walk out of his stall and he did just fine! I got down and looked along the coronary band, which was very soft at this point. I pushed the hair aside and suddenly I saw a big slit in the skin above the hoof! I would say a little less than one inch. The slit was open, but nothing was coming out. It was only in one spot. Then I asked him to walk, and he was 100 times better than earlier that day. His ears were pricked and he was feeling good! I took him to graze and he was perfectly happy. I walked him outside and other than not having one shoe, he appeared 100% sound.
The vet said that he blew the abscess. She said it was normal not to see pus at the site. (Why is that?!) She said to continue icthamol for 3 more days and keep it clean and wrapped (I am using diapers). She said if sound on Sunday, he can have his shoe back on Monday.
I had imagined a big hole in the hoof, and was surprised at the coronary band "slice". I guess they come out in different ways. And, as people have said, he went from mildly lame, to VERY lame, to feeling good. The entire process has taken 2.5 weeks. I am knocking on wood that were definitely on the mend. Band manager called me today and said he was trotting in the indoor arena (were not letting him outside without that shoe, need to protect that foot) She said he wanted to play and was very comfortable.