1. With a fuel leak I would not quickly decide if I would go and dump some more.
2. An overweight landing is basically not a problem if it does not combine adversely with braking and/or flight control problems.
3. As far as I know; if the dumping system is U/S it’s not a no-go.
4. Landing a B 777 at MTOW on a 3000 m runway will not cause any serious braking problems if you do it in an intelligent way i.e. make use of max reversers and use the whole runway to decelerate.