I think you covered the most important topics that most beginners are struggling with.

I definitely made mistake #1 - had no idea about the markdown.
#2 - I think I was quite good at this but there's always new people to meet and interact with.
#3 is something I'm still working on even after being on this platform for more than a year. :D
#4 - just got interested in voting for witnesses, so far I have only voted for @curie and @adsactly but I'll check out people from your list. :)
#5 - in these 14 months on Steemit, the longest I've been away is 12 days in a row. Sometimes I don't feel inspired to write every day but I try to come and read posts/leave comments at least.

What I love about Steemit is that we are constantly learning and growing, I don't think anyone can come to the point of "now I know everything/now I have it all". Thanks for sharing this post and reminding me of that. <3