120VAC is enough to kill some people, or at least interfere with their hearts enough to cause medical/physical issues. Some may just feel a pulsing "bite." Not worth being careless (or even intentionally) to find out which one you are. 240VAC will kill. I should be more precise though: The associated current does the damages, and each human body's electrical resistance can vary among others and/or with conditions.
I do agree that neutral (white) and hot/live (black) wires get reversed quite often enough that it could be a problem. It's why decent outlet testers will cross-check the connections between hot, neutral, and ground.
All capacitors have a tolerance rating that can range from -20% to as high as +80% for aluminium electrolytic’s affecting its actual or real value.
- Electronic Tutorials, Capacitor Characteristics,
http://www.electronics-tutorials.ws/capacitor/cap_3.html
Sometimes caps do have other tolerance ratings, but they are usually marked when they do. The 600uF cap was more than likely within tolerance (min 544uF) while the 34uF cap was definitely not in tolerance and was bad. The 47uF cap measuring 112pF (min 37.6uF) was bad. The 22uF cap measuring 18uF was within tolerance. (min 17.6uF) (Mins given at -20% tolerance)
Changing a voltage filter cap to a higher value has no harm other than it can have a higher "charging" current as it charges to the full voltage available to it. Changing it to a lower value will increase noise and ripple in the output voltage. Changing other caps, such as in timing circuits or frequency dividers with other values can change timings and potentially cause problems. It's usually not an issue (other than cost) to use a cap with a higher voltage rating than what is needed. It is important to observe polarity on polarized caps unless you want it to go
BANG! Design, age of the design, and the materials called for by the design will affect size, leakage currents, and ESR of the caps, especially electrolytic caps.