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?
The thumb test is the fine art of pressing on the tube with your thumb to see if it’s inflated. During testing, I took a pressure reading out of curiosity, and to the touch, road tires feel fully inflated around 30 psi. How pathetically sad—30 psi!—when you’re probably trying to reach at least 60 psi on a mountain bike, 70 or more on a hybrid, and it only goes up from there.
All multi-tools are not created equal, but most with a plethora of features will get plenty of the jobs done. I personally like, and use often, the Lezyne RAP-21 LED tool, which will run you around $30. I like it because not only is it a high quality construction, but it has just about everything you’ll need, plus a sweet mini light. This will give you a chain breaker, spoke wrench, disc brake wedge, and all the most often used Allen keys and drivers. We’re talking a decent number of tools for 1/4 of what they would cost buying them separately.
Many bikes, including older models and track bikes, have bolts attaching the wheels to the frame instead of quick-release levers. If your wheels are bolted on, in most cases you’ll need a 15 mm wrench to remove it. We didn’t test wrenches, because there aren’t that many tiny 15 mm wrenches, but the GearWrench 15mm 12-Point Stubby Combination Wrench is perfect for stuffing into a flat kit and Amazon reviewers seem to think the same. Our experts also recommended the Surly Jethro Tule, but it’s expensive and harder to find.
These folks took me in right away, diagnosed and fixed my stripped handle bar clamps and had me on my way to work in about 15 minutes. Friendly, straightforward, understands the rider's objectives (in my case, how do I get home from work). Not to mention, the fee was reasonable. I have been in many bike repair places in my 6 decades. This is the best.
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.