To add to existing answers, a typical differential signal has the same signal with opposite phase on both signal lines. Your solution 3 has the disadvantage of giving you half the signal amplitude which a differential signal would see, because you only have one signal line.
Professional audio has a workaround for this, because audio applications frequently need to drive single-ended sources such as guitar amplifiers. One half of the differential signal has the actual signal, and the other half is simply driven at 0V - that's driven by the same output impedance (typically the same op-amp) as the "signal" half, not simply connected to 0V. The screen of course is connected directly to 0V. A differential input will subtract the 0V reference signal line from the signal line, which removes common-mode noise from the signal but does not otherwise affect the signal amplitude. A single-ended input will simply see the signal line and the 0V, which does not allow noise to be removed of course, but does not change the signal level.
This is fine for your signal. It does have a downside though (as does everything). Equal-and-opposite signals on a twisted pair radiate very little, which reduces their effect on equipment around them. A single "hot" signal line does not have this advantage, and this could be an issue as you head up into MHz territory.