Re: They land back to earh requires an ungodly amount of fuel
Landing the rocket doesn't necessarily imply you couldn't use a drogue chute to help shed velocity on the way down. I'm sure there are plenty of optimizations they'll be able to do to minimize launch cost, but first they have to successfully land enough times to know they've got that licked.
Doing it once is nice, but there are various things that can happen during the landing attempt as far as different conditions with wind, humidity, temperature, etc. so they can't claim to have really licked it yet. Landing on the sea adds a bit of extra difficulty due to the motion of the waves and having nothing to deflect the low level winds, but if you can do that repeatedly then landing on land would be a breeze by comparison.
Anyway, extra fuel is cheaper than building new rockets from scratch every time...