As far as the boat traffic, I only know that our dive leader said the Aggressor and Peter Hughes boats visit Wolf and Darwin on different days. At Darwin on one dive, there were divers from another boat in the water, but that was the only time during the week we were at the same place with another dive boat.
I was confused about night diving because the Peter Hughes planning guide said no night, but the itinerary said there was. I called Peter Hughes and was told the planning guide jumped the gun and that the itinerary could include night dives. It seems the park regulations aren't strictly enforced. We had two night dives, one in the Anchorage at Wolf Island and the other at James Bay, Santiago.
I don't get seasick, but the crossings were bumpy. They were done at night and didn't keep me or my wife awake. We had pretty good weather so I think we were fortunate. If you get seasick, I would recommend taking medication for the entire cruise portion. The panga rides to the dive sites can get rough.
I wore a Pinnacle Semi-Dry Kodiak, 8/6. I was prepared for cooler temps and the water ended up being warmer than expected. The lowest water temp was 73 at Gordon Rocks. Most of the time it was 78 to 81. I think a 7 would work fine. Take a hood and use it if you get cold. That's what I did. Make sure you have gloves with reinforced palms and finger tips. You definitely will be holding onto barnacle encrusted rock at Wolf and Darwin. We experienced up to 4 knot currents and you need both hands to hold on.
We dove Nitrox for 11 dives until their compressor (Nitrox) broke down. There were 3 straight days of 4 dives a day and we didn't get close to deco. Most of the dives were in the 60 to 80 ft range. However, we did spend some time around 100 ft on 5 dives of 20. Deepest was 120 ft when we were looking for mola-molas (Sunfish) at Cape Marshall, Isabela. I would recommend using Nitrox if available. Ours was 32% when it was available.
I would bring cash in small denominations for tips. In Quito, there were plenty of ATMs and most places take Visa, MC, and Amex. There are entry/departure fees that must be paid in cash. The two going into the Galapagos you may have already paid as part of your total cost. One is $100 and the other is $10. If not included, you pay the $10 in Quito before departing for the islands and the $100 upon arrival. There is a $41.50 departure tax leaving Ecuador for home.