1. Luke uses force grip to choke the guards. I'm pretty sure Jedi aren't supposed to use this, and who the hell trained him how to do it anyway? Yoda?
2. The fact that Luke has this "great plan" to rescue Han, yet all he does is show up and attempt to use the Jedi Mind trick on Jabba. Well thought out!
3. Droids being tortured.
4. Lando, who probably was on Jabba's hit list at one point, manages to sneak in and become one of the guards by using the worst disguise ever! It's so obvious it is him!
5. The singing. Can't say I am a big fan of "Jedi Rocks".
6. Boba Fett's fluke death. Reminds me of how Anakin destroyed the Droid Control Ship in TPM.
7. Han holding no grudge vs. Lando for completely betraying him. I understand Lando is trying to save his life, but you would expect Han would at least make a comment regarding Lando's betrayal after he was released from the carbon freeze.
8. If Jabba had any brains, then why didn't he just get his guards to shoot Han, Luke, and Chewie? Like Count Dooku and the Geonosis Arena in AOTC, Jabba must have really had his mind set on feeding them to the Sarlaac Pit.
9. In general, the whole sequence of events in Jabba's palace is just plain silly and extremely boring. There's a reason why ESB is the best movie.... there is NO Tatooine in it. Tatooine is such a boring setting for anything to take place.
I think it's a safe bet that the suggestion of an entire movie about Han's rescue would require Jabba and his crew done better than what we actually saw. Nobody wants THAT stretched out any further.
I agree with everything you posted except two...why would Lando be on Jabba's hit list? That's a complete guess on your part. And secondly, I think the deaths of both Fetts are the most brilliant things Lucas ever did, on purpose or not. Build these guys up, make them look unspeakably cool, then whack them both as quick and as pathetically as possible. Best "fuck YOU, fanboys" possible...hilarious! I never want the Fetts to not suck. They're useless and I prefer them dead.
Though I'd add the rampant and disturbing sexism in ROTJ as one of my major complaints. I know the bad guy lusting after the ladies is a staple of crappy sci-fi/fantasy and the old film serials, but Lucas takes it to all new heights of creepiness. I don't think it's any coincidence that what we ended up seeing on the screen was SO hateful and degrading to women and his marriage was falling apart at the time.