The standby publisher is a designated node in the cluster that will automatically take the role of publisher if the publisher is lost. You don't want that process to kick in during a cluster upgrade, so for that reason you need to disable that automatic takeover feature (during the time of the upgrade).
Point 2 matches as far as I can see what is in the Upgrade Path to ClearPass 6.8 documentation, with the side-note that I don't see the requirement to first upgrade to the latest hotfix in 6.7 (Direct upgrades to 6.8.0 are supported for all 6.7.x versions when the upgrade is done through the Software Updates portal’s Import Upgrade Image option, or through the Cluster Upgrade portal, or downloaded or installed through the web service.)
I'm quite sure that the license activation patch is included in subsequent hotfixes. Also, if your licenses are activated there should not be an issue.
If you need a definitive confirmation, please work with Aruba Support.