Airlines, including TAM, do have restrictions on individual pieces. On domestic flights, Brazilian airlines seem to have started enforcing the 5 kgs limit for carry-on bags (in our case, even when connecting from an international flight), though enforcement seems to be very inconsistent. Re your checked baggage, I'd phone TAM or go to one of their offices.

I'd expect Avianca Brasil, still technically operating separately from Avianca International, to join the Star Alliance to replace TAM. Gol is not in an alliance but is a code share partner with Delta. Avianca International already has joined Star. Avianca Brasil has a much more limited route network in Brazil than do TAM or Gol, but both of the latter have announced future cutbacks in personnel, so their offerings may be affected.