The cam sprocket turns independently of the cam hub underneath it, so putting a mark on that isn't really going to help you. When you set the belt tension, the three bolts holding the sprocket to the hub will be loose, so it turns independently of the cam & hub.
In order to get your chalk mark in the right place, you would have to put the sprocket on turned a little bit clockwise from where it needs to end up, and then hope it moves back to the right spot once you apply tension. Also hope the crank doesn't move while you're doing this.
It's just not worth it and is prone to failure. The locking tools are on ebay for $15.
Edit: Just saw your new message. Yes, you can take the belt off and put it back on with the proper locking tools. If the belt, rollers, tensioner, and waterpump are still within their service life (or fairly new) there's no reason you can't just continue using them. By not replacing the belt, you also don't have to remove the motor mount.