If you’re going to use the chain whip you just made, you’ll also need a way to get that cassette off. A lockring remover is a must-have; unless you use one of the shady removal methods I’ve seen on the internet—which I wouldn’t necessarily recommend unless you don’t care much about the condition of the wheel after you use them. I recommend Park Tool’s iterations here that cost about $6, but you’ll need to buy the specific one for your brand/type of cassette. (By the way, I’m assuming you already have an adjustable wrench laying around somewhere to use with this tool. If you don’t, well, you’ll need one of those too.)
In addition to the Rema patches, put a new tire tube in your kit. The best method for dealing with a flat roadside is to swap out the tube and save the task of patching for later. If you’re not sure what size your tires are, it’s printed on the sidewall of the tire. This inner-tube buying guide has some photos of where to look. What brand is almost irrelevant as many tubes get manufactured in the same place, so whatever your local shop has behind the counter for under $10 will work fine. The only reason to spend more would be to save weight.
Spare tube: Sometimes, a tube is just too damaged to be patched, or has had a failure such as the valve stem breaking off which isn’t something that can be patched. To save weight and space, I usually keep a lightweight version of the right size tube for my bike. Since one of the first things I do with most bikes that I own is switch them over to heavy-duty thorn resistant tubes, I just take one of the originals and put that in the toolkit.
As you mentioned, it is surprising how often you can get multiple flat tires on while riding, particularly on longer sprints. The tip about bringing a patch kit in your bike repair kit can be incredibly helpful if you’ve already had one flat tire. I agree that all you listed seems like an awful lot to carry, but it’s always better to be safe than sorry, isn’t it?
Bike Radar gives the Pedro’s levers 4.55 out of five stars and claims they’re the “best out there.” (Can we pause to admire the extra five hundredths of a star the site chose to award it? Very specific.) Aaron Gulley, writing for Outside, states, “I can’t count the number of times I’ve snapped cheap plastic sticks, shredded my hand in the process, stomped around cursing in pain for 10 minutes, and then, insult to injury, been tool-less and unable to get my tire off anyway. That will never happen with Pedro’s.”
It has some useful information for basic repairs... not so heavy on the maintenance side but there is some in there. The pictures and drawings are in black and white, but mostly visible. Only a few are difficult to see. However, they are in 2-dimensions and they don't show you HOW to do the thing, they only show you the general area and the part you want to manipulate. The phrasing in the instructions can be hard to follow without a good visual reference unless you're already a master bike mechanic (which you aren't if you're thinking about buying this). So, buy this for general reference and rely on Youtube for video. The two together are better than either one alone.
First, carbon. You already know you don’t need it for your casual weekend pursuits, because you’re not counting ounces the way a professional road racer would. But to quote an article from Velonews, “Remember that professional athletes operate in an entirely different environment than the rest of us. They are all very close to each other in terms of fitness, and they are also all very close to being the absolute best a human being can be. In short, you’re much better off upgrading your legs and dropping body fat through proper training and diet.”
Man, if you're starting out and you know you'll need several components for a bag... just get this. It will save you so much time picking everything out that even if you balk at the price (amazing value, by the way) I bet that if you did the math using your hourly wage and the time spent picking everything out and making sure it fits... you'd save a lot of money and a lot of irritation if you just got this. Just get this.
Road riders need lightweight, tiny tools that can fit into jersey pockets. A lot of those items are made of carbon fiber, which is lighter than aluminum. Other iconic trappings of road riding, like CO2 cartridges and spandex outfits, are also geared toward minimalism, but all of that downsizing comes at a cost. Commuters don’t have to be as concerned with weight, so unless you covet something specific, don’t spend the extra money.
Every expert I spoke to recommended Pedro’s Tire Levers by name. They have a wide body—a different shape than other models we tested—and that prevents breakage, but more important, the broad, flat surface area of the tip helps it stay locked under your tire. When a lever slips from under the bead of the tire, you can end up repeatedly scraping your knuckles on the spokes of the wheel, which is so annoying. Pedro’s levers are small enough to fit into a saddlebag, are sold widely in bike shops, and even come with a lifetime guarantee. If one breaks, Pedro’s will replace it.
Modern bottom brackets use a sealed bearing type construction that keeps water and debris locked out, so they seldom go wrong. Maintenance is impossible so they need replacing when they do wear out. Older style cup bottom brackets need to be re-greased every now and again, and occasionally will need to have their bearings replaced. There are a lot more teeth on the chainring cogs than those on the rear cassette, so need changing less regularly. Cranks usually a solid one piece construction so there is not much to go wrong.