To beat 1 or 2: Click into post, upvote, go back
To beat 4: Open in tab, leave open, vote later
The other problem with 4 is short posts. If someone posts a funny meme or a couple pictures, for instance, that takes a lot less time to "read" than a few paragraphs of text.
Not against these ideas per say, but the reality is users will generally find a way around.
Isn't 3 already the case?
I get it. There will always be a way around the system, but if you combine 1 / 2 with 4, it should encourage more users to read through the story. In terms of beating 4, you could always have an upper end (e.g. > 10 minutes without upvote gets the same payout as upvoting from home page). Bots can be created to beat any complex logic developed, but it could be a beneficial model for the average user.