FOLLOW-UP:
Just returned from Kenya.
1. Did a 2 tank (nitrox) dive with Diving the Crab. We visited the MV Fuongo wreck and the Igloo "reef".
Diving the Crab was excellent. Knowledgeable crew with plenty of staff and very well organized. Their shop was also top notch. I only rented a wetsuit so can't comment on their equipment. They only rent shorties (even though their staff all wore full wetsuits

I highly recommend this dive shop overall.
Note that they use the metric system, which threw me and the dive guide off a bit.
The diving, unfortunately, was less than ideal: windy, seas somewhat rough, with poor vis (maybe 30 ft). I got cold after the first dive and luckily had a cap to wear for the second dive, which kept me just short of shivering, though still cold and uncomfortable.
There was a nice variety of fish at the wreck, but virtually nothing at the Igloo site. Very few fish and no corals. My dive partner told me she saw a pistol shrimp and some nudibranchs. How she did that I have no idea – as I mentioned the conditions were somewhat rough with a little current and poor visibility.
I was underweighted for the second half of the second dive because I listened to the dive master who told me to cut my weight down to 2kg from the 3kg I used on the first dive. My fault for listening, obviously. As soon as my tank got halfway empty I had to fight to stay down and not shoot to the top. Not fun. Due to the conditions and nothing to see I decided to not dive on the second or third days. But I did the Pili Pippa boat trip to the Kisei reef the next day, where I snorkeled. That is definitely worth doing:
2. The Pili Pippa crew was outstanding. Their restaurant was really top notch. The conditions were a little better than the prior day. I didn’t dive with them as I had planned but I feel I made the right decision watching the other tourists’ dive experience. The equipment looked really old (regs, BCs, wetsuits) and the operation was really loosey goosey. I would have worried for my safety, honestly, though everything seemed to go well. I got the sense the dives were all beginner dives (30 ft or less).
The snorkeling: oh my God, that reef must have been SPECTACULAR in years past. When it was still alive. The variety and size of the (now all dead) stony corals is beyond belief. There were some nice anemones and the fish were still very plentiful, large variety, colorful. We even saw a large octopus, a spotted moray, and some giant clams in addition to pretty much every kind of reef fish I’m familiar with.
Many thanks to chf!