In general, if you put any kind of lube on the threads, the torque spec should drop a bit because the lube makes it easier to spin the parts. Over-spinning the parts can stretch the threads to the point of damaging them. If you don’t compensate for the lube, you could end up over-torqueing things. For example, if wheel lug nuts should be torqued to 100 lb-ft dry, it may drop down to 90 lb-ft with anti-seize. As for spark plugs, I don’t know how much it should be reduced, if at all. It also depends on if the torque spec is already tuned for anti-seize. If the official procedure calls for anti-seize, then it’s probably ok to assume that the torque spec already compensates for it.

A beam style torque wrench will work if you can see the dial from straight ahead, ensuring there’s no parallax error in your sight. However, it won’t work so well if you can’t see the dial. If you’re working on replacing the spark plugs in an FRS for example, where they’re down low and against the chassis, a click-type torque wrench might be the only way to do it. Also, keep in mind that torque values change if the threads have any kind of lubrication on them such as grease or anti-seize.

I don’t get why carbon fiber was used in the first place. The composite material is known for its great tensile strength: tensile as in tension, not compression. Carbon fiber is actually also known for being lousy at handling crushing (compressive) loads. If you crush carbon fiber, it’ll fail shortly after.

Going under water would place the vessel under compressive loads, which at a quick glance would be the wrong type of loads for carbon fiber. That’s my initial take on it, however I haven’t spent any real time trying to engineer one.