The issue with the [h] tag is likely a conflict with the version of BBCodes & Buttons Manager that you're using. Please upgrade to a newer version of that add-on, as it has fixed the issue with breaking other add-ons' BB-Codes in a newer version.
As for the slowness, I've narrowed it down to Nodes As Tabs. I've seen this issue before, but was not able to reproduce it on a test install. I haven't seen another report of it for a long time, so I thought maybe a newer release of Nodes As Tabs resolved the issue. It seems you are using the newest release, so I will have to investigate this. I've sent you a PM about this.