On the cloning of Jedi:
- There is no indication in the movies that it is possible to clone Jedi. However, there is no indication in the movies that it is not possible to clone them either. The only character we know can be cloned is Jango Fett, though since the Kaminoans are known as cloners it is likely that he is not unique.
- If you admit materials from the Expanded Universe, then it's pretty clear that Jedi can be cloned: Timothy Zahn's Thrawn trilogy (generally regarded as the pinnacle of EU materials) features a cloned Jedi named Joruus C'Baoth, as well as a clone of Luke grown from the hand he lost at Bespin. Plus, of course, there's also the Emperor's clones in "Dark Empire", but we try not to think about such things...
On the Empire's handling of slavery:
It is mentioned in "The Phantom Menace" that the Republic has outlawed slavery and that the Republic doesn't hold any real sway on Tattooine. Actually, both things are mentioned, hence Anakin's position as a slave.
By the time of "Star Wars", it's reasonably clear that the Empire (the successor to the Republic) does hold sway on Tattooine. And there's also no evidence of human slavery continuing - we know that Jabba still keeps Twi'lek girls as slaves, but no indication of human slavery. It's actually not at all a stretch to think that that is one of the actual benefits that the Empire has brought about - and it's entirely possible that this agenda was largely driven by Lord Vader himself, as a response to his own experiences as a boy.
Of course, we also know that the Empire itself makes use of slave labour - particularly Wookiee slaves used to build the Death Star and Mon Calamari slaves used to build the fleet. (Though, of course, even that is EU material - it's never mentioned in the films.) Hard to imagine that a xenophobic evil empire would be hypocritical, isn't it?
Neither of these is really a definitive answer to the questions asked, of course, merely one interpretation (specifically, mine). However, I'm comfortable that I'm on reasonably solid ground on both of these!