I'd agree with everything here! It's all good advice.
Except for this:
This number would be higher if I also took care of my voting power to be nearer 100% (which I let it slide down to 80% - not good for efficiency) and if I didn't upvote articles that I consciously support without expecting a return.
I would bet that voting at 80% should have almost no impact on your efficiency, unless your power gets low because you're voting for too many low-quality posts. If you let your voting power get very low, I think you'll start losing out on curation rewards because of rounding errors, but 80% is a pretty good target for manual curators. This is not explained well in the whitepaper, but voting at low power isn't less efficient than voting at high power; it's just weaker. You still get the same "oomph" per percentage of voting power.
Hmm... you could be right, but since the details are a bit fuzzy on this, the safe bet is to always have a higher %.
Yeah, one thing is for sure: the higher your %, the more each vote is worth. Can't go wrong with that.