Don't use the word "tone".
You can't target specific muscle fibers. A good analogy I've heard in the past was that, saying you can target one set without hitting the other is like saying you can reach 1000 RPM and skip 500. You can't do it.
The muscles only know they're being stimulated. If it's under the lactic acid threshold (I guess you could say) it will be able to cause muscular hypertrophy. Above that "threshold" you will begin building towards muscular endurance. The lower reps tax the CNS more and, I think how it goes is, teaches your body to more effectively recruit fibers.
Studies that have been done show reps in the 8-12 range to be ideal for muscular hypertrophy. Nothing is set in stone, however.
I think you can do the cardio just fine. You'll earn yourself some muscle, keep in good shape, and won't put on fat. People grow without eating in a caloric excess (non-beginners, as well) - it just depends how far along they are in their gains. If someone's "minimum" amount of muscle (amount they'd have regardless of training) was 12" on their arms, let's say, I feel they could reach maybe 15.5" or so without a solid diet and heavy cardio, and the body would adapt. To break past that point and grow further, you would then have to really start pushing in extra calories. This is what a lot of bodybuilders tend to do. They need all that excess. The body deems all that muscle useless. A couple inches add to your "bare minimum", though, won't be seen as such and is probably achievable through simply training intensely. Don't worry too much about the other shit. I've seen too many examples showing that this isn't necessary.