I dont have much time to answer most of your questions but I can definitely answer one of them.

It is always best to render out to image sequences using any 3D program. Crashes happen, so do power failures. Recovering a broken AVI or QT can be impossible depending on the circumstances.

Render to image sequences. After you have finished with the last frame, create a new scene in Carrara. Import the image sequence and put it in the background. Make sure your rendering size matches the resolution of the original rendered images. Turn off antialiasing and render it out.

This provides you with a ton of options as far as compression, file type, etc. is concerned. It also allows you to preview your animation prior to finish to spot any problems. Just open the images that have rendered and check them.

Rendering 2-3 minutes all at once in any program is a bit much. You are probably going to have camera moves, cuts, etc. It would be pretty boring to have 2-3 minutes of straight animation without some camera moves or some cuts. Save yourself the headache of trying to do it all at once. Break the project up into managable bites. It is best to decide early on which shots are continuous and which can be isolated. You can assemble them later in the cheapest of video editors for post production. Think ahead and you can save yourself a lot of time and headaches.