I don't see any problem in self upvoting. I see it as a problem for the "community" when one only upvotes his posts.
Regarding spamming I also thought of some of my posts with steepshot being spammy and probably they are. "Luckily" I uninstalled the app because it has too many errors so I don't have too many posts of the kind. Sometimes though it is really one picture that I want to share and a title letting people that see it give a meaning of it through comments and start some interaction, but I am aware the general feeling about such posts is of spam.
Regarding re-reading of the post and linking of the sources I do that almost always. Almost...
On the comment topics I admit that I would say some spicy words to some of the "good posts" from the trending page, but I don't wan't to enter the flag and dispute zone. I consider that the Steem platform should do something about this. After all the trending page is somehow the platforms image.
Finally, even if my vote is only 0.01 I really think twice before giving it. I upvoted low quality posts because I saw the effort. Even if the English was bad and the post far from professional that guy/gal put some effort in it and I appreciated the effort and why not believe in evolution of everything.
I don't like long posts and don't read them either. It's a blog after all not a degree thesis. Something between 2-5 minutes of read, depending on the topic, should be more than enough in my opinion.