Rooster Aggression: When does it start and what to do about it?

IMO since he is "freaking out" when you pick him up, you don't need to do anything. He's already accepted you as the alpha roo. No subordinate roo likes it when the alpha roo gets after him.
Of course that doesn't mean you won't face challenges later on, but I'd take a watch and see approach. He may never give you any trouble at all.

 

I have two RIR roosters, Buddy and Big Red. Both are 20 weeks old today. Big Red has not shown any aggression towards us at all. But a couple of weeks ago, Buddy tried to push his luck. He jumped at me several times, on both my daughters, and at one of my sons. But, I read a post on here that said you have to show the roos who is actually boss. The suggestions were made to pick up the roo and hold him until he calms down, if he shows aggression to you. We did that to Buddy once. Since then, he's not even made a gesture as if he's going to attack.

 

They aren't all aggressive. Yours may not be a problem.