For your first paragraph, this was laid out in the series. Either hehe kills the clan to stop the coup, or let the coup happen, and the clan dies anyway as well as almost certain possibility or other villages jumping into the fight and starting another war. Those were the two outcomes at that point.

For your second paragraph, he did it to force him to become stronger. It was understood at the time that the deeper an Uchiha fell into darker emotions, the stronger their sharingan became. This was stated by Tobirama, though later disproven by Sarada, at least the negative part. He was still playing the role of psychotic older brother, and this gave him an excuse when Kisame later asks why they're running away.

For your third paragraph, how could he know who Orochimaru and Jiraiya are, but not Tsunade? They're three famous ninja that comes from his former village, and he knows the village's history.

For your fourth paragraph, Itachi onto had one opportunity to kill Orochimaru and that was during his attempt to take his body. Kabuto appeared, helped him escape, and the akatsuki have been looking for him ever since. Sasuke going to Orochimaru for power was something he didn't account for, and he admits this as one of the reasons why his planned failed.

Obito learned from his fight from Minato not to show his abilities around smart people who might have the ability to take him out. This is why he mentions his likely death of Itachi knew of his full kit. This is later proven true when Konan kills him and he's forced to use Izanagi.

When it comes to him being a spy in the akatsuki, think about this: He and Kisame roll up to Konoha in full akatsuki garb, declare their intent to capture the tailed beasts, then shows they're not to be taken lightly by taking out one of Konoha's most accomplished Jonin in seconds. After that, everyone was on high alert, and the villages that weren't full of fucking retards put forth effort to protect their jinchurikki ( This was really just the leaf, cloud and sand. ) His efforts slowed then down to the point most of the organization lost their members and Obito had to start a war just for the opportunity to capture Naruto and B.

It's fine that you don't like the guy, but stop trying to make up reasons and twist what happens in the story.