You seem to have learned many of them. Anything else might be just arguing. But in typical BF fashion, we like to argue and just like your first century, sometimes there is stuff to be learned in the arguing around here. But mostly the differences for why we argue is that it's not one size fits all.
1) Carry water with you. Always! I take two bottles for all but the shortest of my rides. And even that ride gets one bottle. But most of my rides are 90 minutes or more in hot weather. Any over 2 hours and I'm taking a 3rd bottle or will know where I can stop and get more. I take a gulp or two of water every ten minutes. Though many probably go fifteen minutes between sips. It's hot and I sweat a lot where I ride. I also put Calories in my bottle. Essentially sugar. It keeps me from having to deal with things that are in wrappers and fiddly to undo on the bike. Though some make a little bottle you can keep in your pocket that holds gel you can buy to get your carb's. Though some grape jelly or strawberry jam will probably work almost as well.
2) I too saw the benefit of CO2 for getting the tire aired up quick. Frame pumps on the top tube take up space and hinder getting bottles in and out on some bikes. Mini pumps just take too long. I seldom flat unless my tire is worn out and I can see the air inside is about to show. So I've wondered why I even carry the CO2 inflator and cartridges along with the patch kit. I've seen mini pumps laying near the trail that I assume someone got frustrated with. So they have litter potential too.
3) I wear cheap jersey's too. A $18 dollar jersey I bought 8 years ago is my favorite. Held up better than some of the more expensive ones. But spend some money to get some decent bibs or shorts. I use Pearl Izumi. The middle tier price range is worth the extra cost from their bottom line bibs and shorts. But some don't like PI or get good use from them, so there are plenty of others brands out there.
4) I use sun sleeves. But I still have to put some sunscreen on the back of my neck and ears. And the tops of my knees as well. For some reason my shins don't get much sun. I guess its the sun being high when I ride.
5) see #4.
6) There is a difference between how a hammock saddle works and the other saddles more typical for a road bike. So if you got a more typical saddle, then you need two to three weeks to get use to it. Even today, if I don't ride for awhile or I do a bunch of short rides and then a really long ride, my butt won't be use to the time in the saddle. And it'll hurt for a good week or so. But only when I mount the bike. Once I get to pedaling all is good.