Frequency range is 0.5 to 2 MHz. Current is under 5 mA. I don't know what the maximum voltage will be at the moment. Due to resonance it could be significantly higher than than the supply voltage which is 12 volts. However I did use a regular DIP switch in an early prototype of the circuit, and had no problems with it.
Good news: After my last post, I had a look at the parallel inductor arrangement, and after playing with the numbers in a spreadsheet, it looks as if I can get quite a good workable range. The increment between steps is no longer constant, but will be a constant percentage, which may in fact be better. I need to play with the numbers a bit more.