Creating useful content will always be the number one way for you to increase your hub author score. I've been at 100 several times, regardless of whether or not I was actively commenting on hubs or in the forums. This typically happens when I'm getting the most internal traffic from Hubpages and the most feedback on my hubs.
Commenting will also help to increase your hub author score, so make sure to keep commenting on interesting hubs that appear in your feed. My hub author score on a satellite account right now is 91, however, and I do all of my commenting from this account; Let that be an indication to you of how important the useful and updated content is to Hubpages!
ETA: It looks as though your hubs may be a bit on the short side. Try adding more capsules and make sure to use capsules that encourage engagement. Polls are an excellent way to keep users on your page because people are inclined to vote, which takes a few seconds longer. That break is sometimes enough to get them reading all the way to the end of your page.
You may also want to use more text capsules and break the content down a bit more. See if that doesn't help!