Why is 7 the best you can shoot for? France is at 5 tons right now and even French people consume a lot more than they need to. They just aren't as blatantly overconsuming as the USA is. Sweden is at 4.5, Switzerland is at 4.7, UK is at 5.5. And that's with current tech and a LOT of things they could be doing better.
It should be closer to 2-3 tons. And that's possible with better tech, but ONLY if consumption is seriously cut back too. Both need to happen, but the consumption reduction is both easier and more important. tech alone will not even come close to getting us there.
I'm really confused as to what you're suggesting the alterative is. Give up?