I don't see a problem with the Elvish.
A proper director could've gotten the right emotions across, whatever the language
I was fine with the Elvish. Taylor had said he wanted the language to establish the Elves as having their own deep history and culture separate from the other realms. I thought it was cool that they were able to develop an entirely new language and that the actors were able to learn it in such a short period of time. I'm still wondering why Asgardians speak English. At least they aren't speaking Middle English.
and I agree with Mjolnir up there^ that Thor was more changed by the end of the film than Loki.
The problem was, that change wasn't earned, at all.
There was, what, one line of him disagreeing with Odin's rule??
More of that court intrigue and showing the sacrifices Odin has to make, and the "how could my father do such a thing" type scenes would've helped a lot to make Thor's arc more convincing.
Instead by the end, my only thought was, "you still have the bridge, and you saved the day, and you even had to bring Natalie-Jane Foster to Asgard to do it, so... why can't you protect earth from Asgard??"
He changed, yes, but it made little sense as to why
I agree with Mjolnir as well. But I don't feel the change wasn't earned. There is more to it than that one line of dialogue.
Thor's arc doesn't begin in this film. It begins in the first. This film is just continuing that arc.
In the first film, Thor's cockiness brought him low and during his stint on Earth he had no idea what Odin had in store for him nor did he know what he wanted to do with himself. He was lost. During this vulnerable period, he was moved by Jane's kindness and her devotion to her work showed him strength where formerly he would've seen weakness. He learned to appreciate the value of all life and was willing to sacrifice his own for it when his new friends and the people of Earth were threatened by the Destroyer. His sacrifice restores Odin's faith in his son and Mjolnir becomes his once again.
Even though he is now restored to his birthright however, the beginning of this film shows that he's still lost. He's dutifully restoring order to the Nine Realms as son of Odin and heir to the throne but he's clearly restless, pining for Jane and uncertain of his role - which is why he can no longer revel with his friends and looks for Jane every night from the Bifrost. Even Odin recognizes it in their first dialogue together.
Thor regards Jane very highly. Later on when Odin recounts the tale of the Dark Elves and Jane asks what happened to them, the Allfather said that Bor "killed them all" this does not sit well with Jane.
Then comes the confrontation you reference where Thor seeks to avoid further bloodshed via his ultimately foolhardy plan of which Odin does not approve. Odin is prepared to sacrifice every "last drop of Asgardian blood" which prompts Thor to ask how is he different from Malekith. This is the same Thor that earlier destroyed the Bifrost to save the Jotuns, a whole other species that he would've killed with his bare hands. Thor clearly doesn't want anyone to die. Thor wants to save everyone and thinks he can. But you can't be king and not be willing to risk the lives of others. In the first film, Loki said he had gone soft.
Then there is the moment between Loki and Thor on the skiff. After Loki says "satisfaction is not in my nature", Thor states that "surrender is not in mine". And after almost losing Jane and being told by everyone that it will never work, he's no longer willing to be apart. By favoring Midgard, he's trying to "do it all" - protect the realms but be with the girl he loves.
All of it's interconnected. Thor is drawn to Earth because of Jane but he also is just not plain ready for the throne. I'm sure Thor's denial of the throne is not without a little selfishness. Even in the comics he was kind of irresponsible at times. In the end, he will have to rise to his duty. I'm looking forward to seeing how it all shakes down.
You're right that they could've flushed it out further though. Stuff like this is where I feel the film was too compressed and would've benefited from a longer run time. The cues are there but it's a short film covering a lot of ground with concurrent plot lines and those cues are easy to miss.
I love this film but the short run time is my biggest complaint. Iron Man 3 and now CA:TWS are both two hours plus. I hope Thor 3 gets its proper due.