I'd have some suggestions. For the spam, well, there's always gonna be spam, especially if there's money involved. My solution is follow people that make quality content that you enjoy, upvote them, and just skip the spam. Censoring them is not a good move in my opinion, this always gets abused eventually. The #indroduyourself being abused is annoying, and it does mean some people get more noticed than others. I know I put some work in my posts and don't get much traffic, but when someone if alot of steempower comes by, they likely appreciate it, and those that do follow me get some quality content to read. So, that's ok :)
Self voting should still be on, but it should be allowed for comments that generate responses to it; if it has replies, only then should it be allowable to be self voted, that's my compromise solution :)
On the notification aspect, I really think that should be a thing, and regarding comments unrelated to the post, well, what can you do? Just ignore them.

It's good to see you started a discussion, and steemit does need some tweaking, for sure, but overall, I think it is a good platform. Here's hoping for more support and a better future for it and its users!