He has all the power he needs. He told teams he will not sign. So it will become a wasted pick. A player who does not sign can enter the draft the following year. So basically he told teama if you don't want me at these spots your not going to get me at all, which is fair.
If it is that easy more players that don't like their draft position would hold out. It sounds good coming from the agent, but if you're a player would you find it easy to turn down 500K per year and go a full year with no pay? I would probably try holding out after playing a year when I had money in my bank account.
There is a really good chance that if he re-entered the draft that he would not be a 1st round pick anyway. Players lose their luster to teams when they have not played in a year.
It's a fascinating situation and I feel bad for the guy if he didn't do anything wrong. It will be interesting to see what happens.
If a team does draft him and he is contemplating not playing, they would likely offer to give him a new contract after the 1st year. The contracts are set for draft picks, but IIRC teams can give them a raise after the 1st year. Now you have this kid facing a choice of taking 500K per year and a verbal "promise" to give him a raise vs sitting out a year with zero pay. That's really hard to do unless he comes from an affluent family.