Earlier quoted context omitted.
Fusion isn't a silver bullet even if it works. If it costs more than solar+battery then it's worthless.
No, this is way too shortsighted. Fusion allows us to use other energy sources than our own sun, which means it's essential for viable space missions, and we won't need to compete with the rest of nature (including agriculture!) for our energy needs. Hydroponics with fusion technology allows us to produce food without relying on the sun at all. I'd say that alone is worth the investment.
As for the future, beamed power will work out to interstellar distances, so energy sources other than our Sun (and other stars) aren't necessarily required.