Congrats on your growth and thank for the witness vote!

According to the report on HiveStats, I have a Curation APR of 0.61%, but I think there is a mistake here

Yes it is a mistake. When you power up, it calculates the previous curation rewards CR, that were based on a smaller amount of HP, and when compare to the now bigger amount, it distorts the APR. Example you had 1000 HP, and 7 days with 0.3 HP in CR daily. You power up to 5k HP, and now it still calculates 0.3 HP daily, but on much larger principal. It will fix itself in time.

Regarding CR advice I can only tell you to keep your voting power above 80%, ideally between 90% to 100%, but never 100% :), and don't vote on post older than one day.