I agree on all points and this is really all that is necessary to fix copyright. The original intent was to protect the creators of artistic works and at the same time give them incentive to keep creating. It was never this monstrosity that we call copyright today. Instead, the ridiculous time periods granted is hardly an incentive to continue creating but rather to create one or two smash-hits and then retire. I won't even go into the corporate mess that has arisen.
A comparison I've been thinking about is comparing with pharmaceutical patents. The pharmaceutical industry is super-high risk as the average pharmaceutical costs around $1b to bring to the market and yet 9/10 candidate drugs fails to get there. Even getting a drug out on the market is no guarantee for success. The patent right is only twenty years because pharmaceuticals are seen as essential to the general well-being of society, but it works. So why the hell should an artist (and then a corporation after the death of the artist) should have 70 years to collect profit when the risk is nowhere near as high? Not to mention that the artist is unlikely to be alive for that entire period of time, or as in the States be dead for 70 years.