The extent of my knowledge is best summed up by watts = volt x amps.
With that statement in mind, I will say this:
Generating 100 volts at radio frequencies is quite easy especially if you use older thermionic valve (tube) technology.
Measuring that 100 volts at (say) 100MHz can be a bit problematic. Due to standing waves, you could have 100 volts at one point on a pair of wires and 0.75 metres away on the same pair of wires you could have 0 volts.
To do experiments with that 100 volts at 100 MHz, you will need a screened room unless you want to jam every FM broadcast radio station in town.
Generating 100 volts at 100 MHz with several hundred watts of power so that you can drive your halogen lamps, is not an easy task, especially for someone with very limited knowledge of RF electronics.
It will also get very expensive, very quickly.
All in all, I think that your idea is a bit of a non-starter.
As for the measurement which you have made with the coil on the induction heater, consider that your meter will probably (almost certainly) not respond correctly to the "harmonics" which were displayed on the oscilloscope. The meter display will be wrong, which is why you appear to be getting power from nowhere.
JimB