I don't think the main problem here is random terrorists cutting power to Europe by blowing up a power line tower. The real problem is that nation states that control the Sahara haven't proven to be stable (Syria, Egypt), or don't always have great relationships with Europe (Algeria in the 90s).

As to points 4 and 5, although storage and some backup capacity is reasonably feasible, this would mean that Europe could very well be forced to go to war in short order to get their full power supply back if a rogue organization gained power in North Africa.