That's awesome. I only have autovotes on to follow curation trails (I had to make sure I don't self vote when I'm curated by the ones I follow), I also have autovotes for projects I support like ocd or curangel. However, I stopped autovoting for individuals.
About manual curation. I cannot do it everyday, but on the weekends and some evenings I can. I follow trails at VP> 95 and eventually I want to stop supporting most curation posts when I have a good method for curation.
My % is around low 40s because of supporting all these popular initiatives. If I stopped I feel it would jump to mid-50s quickly. I could probably get it to the 70s if I only manually curated and only voted for posts I know are ideal to curate for efficiency.
I think in your case, you may have to start re-steeming a few to get it up even higher since your score is already fairly optimal.
However, at that point, the biggest issues is that you may be skipping the content you find interesting to favor content want to vote for just to get your efficiency higher. In this case, it may almost make sense to split your SP between two accounts - delegate to a new curation only one and keep some of your VP in a content consumption one. Just a thought.