Urk! So many ways to answer those two questions...
Unfortunately, since my answers would be based on scientific research, the average JW would look askance at me for stating: "No, of course "Jehovah" didn't create the earth to last forever because:
(1) "Jehovah" himself is only one of many gods in the bible, and said bible is ONLY around 3,500 years old. When one compares that to the age of, say, the Acheulean Goddess totem or statue found in Israel, which is AT LEAST 235,000 years old and may be as old as 800,000 years old, one can see that this "Jehovah" is a mere "Johnny-come-lately" deity - in fact, is one of the most recent religious inventions on the face of the planet!! [Not counting Mormonism and Scientology, as well as Islam...]
(2) The earth will actually cease to exist (according to the latest scientific estimates) sometime in the next 2 billion to 3 billion years... That means the earth will exist for a long time, but definitely NOT "forever"...
Then I could go on and on about how this "Jehovah" is a mis-pronunciation of the Tetragrammaton, that its correct pronunciation is actually closer to "Yahweh" than anything else, that they don't really know how 'his' name was supposed to be pronounced, that there are actually AT LEAST THREE 'gods' in the bible ("EL", "YHWH", and that Three-In-One Eleusian-Greek-influenced version in the "new testament"...), that the 'old testament' YHWH god was probably generated in the Isra-EL-ites' minds because of their superstitious misunderstanding of how the earth REALLY worked (they mistook erupting volcanoes as manifestations of their 'god', several times), and so on...
Whew...
As to that part about "Satan" ruling the 'world', that's probably derived from a Zoroastrian belief that existed in Persia - among other areas - several hundred years before the 'new testament' was a gleam in a fanatic's eye... And how "Jesus" may not have ever existed - the Romans, who were scrupulous record-keepers, NEVER mention him during the time period that he was supposed to have 'lived'... He's only mentioned AFTERWARDS, as the Christian cult began to grow and gain power in the 2nd and 3rd centuries...
And on, and on, and on...
Wish I could be of further help to you...
Zid