Powerful ones do.
Never seen one. Domestic microwave ovens are well shielded.
Only in the sense that some nuclei have a magnetic moment. If you bash them at the right frequency in the right magnetic field you can get the magnetic pole rotating at that frequency. There no fancy resonance theory involved.
I've got a Ph.D., in chemistry and while we got lectures on nuclear magnetic resonance, there was no fancy resonance theory involved in that either.
"Resonant bonds" are just a bizarre way of describing de-localised electronic bonds. Benzene has six carbon atoms arranged in a flat hexagonal ring, with one hydrogen atom hanging off each carbon atom . Traditional descriptions say that there are three double bonds and three single bonds around the ring - but that would make the three double bonds shorter than the three single bonds, and all six bonds are of equal length. Lecturers who were stuck in the traditional mind set liked to claim that the molecule resonated between two states where the double bonds and the single bonds swapped places rapidly. It was nonsense, but it kept them happy.
It's a famous example of an under-damped mechanical resonance - nothing more.
You can build in dampers to prevent the resonance from storing a lot of energy or distorting the structure beyond it's elastic limits.
These days mechanical engineers rely on computer simulations to let them anticipate this sort of problem.
Your idea of what might be "remotely useful" reflects more wishful thinking than any clear grasp of what is actually going on.