He still could of chosen a better actor and had less cheesy lines.

That could be one point of view, and a valid reason for the change, but it does seem to go against the whole idea of Vader/Anakin's redemption and return to the light. The whole point is that at the end he has turned back to the light side of the Force. Therefore his Force ghost should really be the older Anakin to reflect the fact that the older Anakin had been redeemed, rather than turning back the clock 20 years to when he was last a good guy it should be celebrating the fact that he was now once again a good guy. Of course this is just my opinion and the argument easily goes either way on this subject.

There are indeed inconsistencies in the OT, but none of the examples you give here really qualify. Grand Moff Tarkin was superior to Vader at the time of A New Hope (from a certain point of view). The New Order at this time was still evolving, and despite the fact that obviously as far as Palpatine was concerned Vader was second only to him, he still had to keep the military in line as this was the key to his power over the galaxy, he still had to maintain all the beauracracy that any leader has to deal with to keep the cogs of his new society turning, don't forget that many (if not almost all) still didn't know about the Sith, let alone that he was in fact one. So yes he pandered to the needs of the Military, and the politicians for a time, remember Palpatine has only just dissolved the Senate during the time of A New Hope. Vader had no military rank and therefore fell outside the chain of command, officially going by the title of Emperor's Emissary, almost little more than an advisor and the eyes and ears of the Emperor (at least as far as the Military High Command was concerned). The Military had little respect for him at this time as he was little more than the Emperor's favoured pet. So  this is where Tarkin comes in, who knew better. He was a member of  Palpatine's inner circle, being a close conspirator with Palpatine for some time. Being in the chain of command Tarkin at this point was definitely the guy in charge on the first Death Star with more authority than Vader. It was only after the Empire's defeat at the Battle of Yavin and the Imperial Navy has to go seriously on the offensive that the kid gloves come off. Similar to the Emperor's taking of power in the Clone War crisis the Emperor increases Vader's authority giving him a fleet with which to pursue the elusive Rebel threat, and the Sith now show their true colours leaving the Imperial Military in no illusions as to where they now stand in the pecking order.

As for Lando and Chewie never returning from Jabba's Palace?  This is true to a point and also due to the limited knowledge that C-3PO had at the time, remember that he has not been told all of the details of the plan to rescue Solo, in fact he is pretty much totally in the dark regarding the plan in it's entirety, probably for the best considering he could spill the beans in any of six million forms of communication. Lando and Chewie did indeed travel to Jabba's Palace, Lando is still there in disguise after months spent undercover getting into Jabba's entourage of thugs and villains. So truth be told he has never returned from this awful place as he is still there.  As far as Jabba addressing Lando by name? I have no idea where you got that from, but he doesn't, the guy is in disguise as a skiff guard, and doesn't break from that disguise until the battle over the Sarlacc pit. As for Chewie this is where the failing comes in 3PO's knowledge of the plan, the last he knows of him is that he and Lando were heading to Jabba's Palace to rescue Han, so as far as he knows Chewie never returned. In reality Chewie rendezvous with Leia and together they facilitate their way into the Palace. Look to the comics and novel of Shadows Of The Empire for more details regarding this.

I don't really see a problem with this, celibacy is not just confined to the religious institution to which you refer. The closest real world parallel to the Jedi would be far eastern warrior monks, and it is this model on which Lucas based the Jedi and principles of the Force (before all that Midichlorian rubbish ) amongst a mish-mash of other religious ideas and mysticism. Celibacy is seen as a way to focus the mind and body in these instances free from these distractions they can reach enlightenment or become one with the Force or whatever. This totally fits in with old Ben's comments about the Jedi in the OT and only heightens the air of sacrifice and commitment that would be associated with such an enlightened and spiritual organisation such as the Jedi.

Sorry for the long post, guess I was bored on my lunch hour.