You may need to do more of your own research to satisfy your own doubts and questions to an extent that makes you comfortable. Clearly what I have said isn't doing it for you, but let me add:.

This is the official site for the Argentine side of the park. In at least one photo, you can see the " walkway on the ARG side that, goes out to the edge to look over the falls", like a bridge over part of the river.
Iguazú Argentina 2016 - Parques Nacionales
I did state exactly where I thought a person might get wet, but you seem to be ignoring my comments for your own imaginings. The walkway in the photo is different from the one on the Brazilian side, which is on a kind of plateau in the river between a fall of water above which emits spray and the one below.

As far as buses, you can take my word that they exist or do some research, probably in Spanish, to try to find a site with schedules. They are local buses that run on a regular schedule. But perhaps a small village like Puerto Iguazu does not see a need to pay for an internet site for such things. (My own trip was based in Brazil and I did not have time issues, so didn't really care to spend time finding out. I personally would not choose to spend money on a one day trip to the falls.)
Your post sounded like you would be staying on the Argentine side for the day, inside the Argentine park. If the bus isn't at the entrance when you decide you need to leave to catch your flight, ask staff when it might arrive or take a taxi from there. The airport is not far from the park entrance.