2) Yes... but... there are two ways to "get the video into the computer."
The first process flow is what you are apparently used to. Connect the camcorder to the computer with a USB cable, put it in play/PC mode, launch the video editor and capture/import the video. iMovie may prompt you or automatically run through this, but this is what happens. In this process, the video is decompressed during the importing process and uses up all sorts of space on the computer hard drive. In this case, the video editor uses the camcorder and computer to decompress and transcode the video to a video editor useable file.
The second method copies the compressed, source files from the camcorder. This is basically just copying files. They stay compressed in their original state. No transcoding, either. To just playback these files, a media player is needed that can deal with the MTS files. Quicktime player cannot - it is included in your Mac. But VLC Player from www.videoLAN.org can. It is open source. If you decide you want to work with a specific clip in iMovie, the clip needs to be transcoded to a useful format. Both MPEG Streamclip from www.squared5.com and HandBrake from www.handbrake.fr are useful transcoders to have. After the file is converted to a MOV or MP4 format, quit the transcoder, launch the video editor and drag the MOV or MP4 file to the video editor's "library" and edit as though you just imported from the camcorder. Do not do anything with the original MTS/TOD file - it is your archive.
So... just because the original, compressed, files are in your Mac does not mean you can't do anything with them. You just need a couple of applications, beyond what is currently in your computer, to do what you want.
When the video editing project is complete, you render the video - this includes compressing at various amounts depending on what the video will be viewed on/with.
3) Right - but since we can edit later, you can start now and not miss anything... just have some catch up.
4) How I would do it:
Import the video from the camcorder to the video editor. Do the editing, all done, render to a couple of different files for the different audiences, delete the video editing project files. Copy the camcorder original video files to the computer for "archive/back-up".
I *think* the easiest will be to create a folder directory structure that has the year, and inside that folder, each month. Inside the folder will be the compressed video files. We can spend more time on this later... You can name the files with something useful - like the date and topic or create another subfolder by topic if that makes sense.
So the suggested directory structure - folder names - looks like:
Basically, doing both ways described in (2). In the above folders the copied, original compressed files are stored. You can also rename the files so rather than numbers, they have a useful name - but keep the MTS file type/extension.
If needed, set up something similar for the "Viewable" video. But your iTunes/AppleTV should take care of that. I've not used AppleTV extensively, so you are the expert on this.
My tapes have been collected over about 10 years, and most are probably 3/4 used... most would be considered "home movies": child's school stuff, outings to the zoo... but this is my hobby, and there are music videos of local bands performing, local non-profits that would not normally be able to afford decent video - and I've done some stuff for a few local small businesses...
"Media server" - like AppleTV. In the non-Apple world, http://en.wikipedia.org/wiki/Media_server
Today, I have a couple of options for playing back home video...
Connect a Mac to the TV with a VGA cable;
Play a (standard definition) DVD using a regular DVD player connected to the TV;
Connect the camcorder to the TV and play back the tape (using different connectors);
Transcode and compress the high quality video to a MP4 file suitable for iPhone/iPod (sync with iTunes);
Upload to YouTube, Vimeo or other video sharing site - make it public or private - viewable on a computer. And the DVD and edited/rendered video file are viewable on the computer, too.
I don't see the *additional* benefit I get from an AppleTV box other than the connection to iTunes (movies), but I just connect a Mac to the TV with a VGA cable. More expensive that the AppleTV, but the computer's already here...