iCloud alternative for a calender sync
Update: According to developers/macrumors local sync is back in the latest beta of iTunes, and will hopefully be back in the next release as well.

Like you already said - being worried about security issues when you run the server locally is reasonable. You probably will never get your local server as safe as apple has made their iCloud Server. 
I honestly don't think your calender is so interesting that anybody would want to hack it, bur that's your decision after all. 

I currently don't know of any app that syncs via usb. Sync mate doesn't work under mavericks, but they said an update would come in "winter" this year. 

If you want to go local, I'd recommend using OS X server.