I think you used up your limit of words in the title.
1- Possibly, but I doubt it. Ammonia smell is comon in urine. As long as you don't smell like full strength ammonia you should be OK.
2- Cottonwoods are soft enough you shouldn't need the auger. Just make sure you get through the bark and into the wood before you put any weight on the step.
Don't know anything about the other gizmos, sorry.