Man there is no way you can keep up with 5000, or even 500 Active and engaged followers. You have to pick and choose. And no matter what you chose to do, people will holler at you that you aren't doing enough.

There is a sense of entitlement to Steem that should not be allowed to succeed. Work should be what is rewarded. Proof of Brain. There is nothing at all wrong with the way you are doing it. Keep on Manually curating.

So a couple of the options....

Do nothing, don't vote, don't curate, just sit on your SP. Plenty of people do this, and it doesn't accomplish much for anyone. I don't think this is the option for you.

Manually Curate, as you do. But maybe spend more time considering the person you are voting for and what your upvote means to them. Someone who has been active for a year and already has a lot of success, your upvote might not mean as much as it does to someone who has been here a short time and has had little success, but is trying really hard. So maybe adjust percentages. Still upvote the guy who has been here forever, but upvote him 20% and save 80% for newer users.

Delegate SP to someone you trust to Curate on your behalf. I've seen more and more whales with smaller and smaller personal upvotes because they are delegating to OCD, or Curie, or a friend who curates on their behalf. It keeps the SP working, however does not benefit you with curation rewards.

I'll tell you one thing I would love. When you have an active and involved following like you do, if you see someone who is really trying, and whose blog reaches out to you, a resteem is worth more than an upvote. Having those extra eyes that might end up following the newer user because you resteemed their post, that's a huge reward. Obviously this is more of a time investment than just giving an upvote, so might not be feasible for you. But maybe you pick a couple of people a week who really strike you in your comments, take a bit to visit their blog, and pick a post to resteem if it impresses you.

As you said, you give a lot more rewards in the gifts you send out and the efforts you make. No one should ever be questioning how you use your vote. But they will. And you asked for thoughts, so there you go.

Bottom line, do the best you can with the time you can give it, and don't sweat the small stuff like whiny followers. :-)