The first thing that strikes me about your trip is that Rio is just out of the way compared to everything else. I understand there is good reason for you visiting Rio, given its status and Carnival etc etc. However, if you haven't booked your flights yet I would recommend starting your trip in Rio and working South and West from there towards Argentina, Bolivia and Peru. Otherwise to go from Iguazu Falls to Rio and then back to Bolivia (possibly via Cordoba?) seems a bit much backtracking.

On the plus side, what you have planned for three months in terms of number places you plan on visting seems ok, i.e. less than 10 places. In fact you could probably squueze in a few more without being overly rushed. For example when in Rio why not take a diversion to Ilha Grande and/or Paraty. Or look at Potosi and/or Sucre when in Bolivia. Same for Lake Titicaca in Peru.

In a nutshell, have you booked your flights yet? When you tell me this then I can tell you more if you so wish.

I agree with pgriffin - I'm not sure if you are going to Rio solely for the Carnaval or to see more of the city. The reason I ask is that if you are planning to be in Bolvia, the Carnaval in Oruro is amazing and well worth a visit. but book your accommodation well ahead as prices go up and availability down although i had a friend who did a last minute booking through a guy on Couchsurfing who rented out beds in a school and all profits went to the school. Potosi is well worth visiting and Sucre only 3 hours away for a city chill. And i wouldn't miss Lake Titicaca for the world.
If you need any more help let me know. If not, have a great trip!