Well, this avidemux3 was promising, but fails badly:
* Can not remove commercials in the middle. It only can trim the start and the end.
If you have a video without commercials, your way was the right one. If you want to remove commercials, you have to mark the commercial and then press "del" or go to edit->delete. Repeat for every commercial and the start/end you want to crop.
* Produces no sound. * Can not parse the input stream, it aborts somewhere in the middle.
I can only guess that the recording has some problems like missing frames. For the audio: avidemux3 can have problems encoding audio when the audio tracks change during recording. For broken files you may have a chance to fix it by cutting it with avidemux and select copy for both Video and Audio output. Then try to postprocess it with HandBrake. Or try to preprocess it with HandBrake and then cut it with avidemux3.