You definitely run the risk of harming your cycle fish; it's unavoidable. That's why super hardy species that can hack this sort of thing are best. It's kind of hard to get around that unless you do a fishless cycle. Still, by keeping levels low, you're most likely extending the time measurable ammonia will be around, which stressing your fish in a similar way. By doing an aggressive no water change cycle, when it's complete, the tank is CYCLED and future additions of fish are very unlikely to cause any ugly spikes of anything dangerous. What you want is a bacterial population explosion.
I would definitely wait on any new additions. What you have going now is more than enough to cycle it. Just wait, measure and watch. The day the nitrites vanish (and they will vanish seemingly overnight), do a 90%+ water change (carefully since you have fish and I would skip the gravel vac for a couple months (or forever) since you are presumably planting), double check your water perimeters, and go hit your LFS and get something cool. No worries or doubts at that point.
The only other consideration is that like any other population, your bacterial population will slowly adjust to the amount of ammonia and nitrite is has to feed on. So, the days immediately after the nitrite vanish, you will have an extremely strong bio filter. If your tank stays will a super low bio-load for a longer time (no new additions), you won't have to re-cycle it, but you will want to make future expansions to the population in relatively small groups a week or so apart to allow the bacteria population to keep up with the increase in nutrients.
Get that guy a cap and a speedo!