Hi, welcome to the forum. Glad you joined.
I have 5 hens and 1 rooster. If he is friendly now at 20 weeks, will that change?
At 20 weeks he is still an adolescent cockerel. He will go through some changes as he matures. No one can tell you what those changes will be, whether they will be good, bad, or negligible. If he hasn't already (and he probably has) he will become the flock master. He will keep eggs fertile. A good rooster should take care of his flock. But there is a difference in an immature cockerel and a mature rooster, just like there is a difference in an immature pullet and a mature hen. It can get pretty rough
as they go through adolescence.
Will he remain friendly or become more stand-offish as he matures? I don't know. Will he become human aggressive? I don't know. With living animals and behaviors you just don't know what will happen.
Also, is it true that if you have a small flock, the rooster will “wear the hens out”?
Not always. Often not at all. Some people keep one rooster with only one or two hens and don't have the bare-back hens, over-mating, or other problems. Some people keep one rooster with over 20 hens and do experience some of those problems. Again, with living animals you don't know what will happen when it comes to behaviors.
Typically things can get pretty wild while they are going through adolescence. The cockerels hormones are raging, he does not have any self-control, and the pullets aren't mature enough to do their part. If you can get through this phase, they typically mature into a peaceful flock. Not always but usually.
Is it best to get rid of him now before anything changes?
I don't know you goals, especially pertaining to that cockerel. Why do you want a rooster? The only reason you need a rooster is if you want fertile eggs. Everything else is personal preference. Nothing wrong with personal preference, that can be a strong motivator. I generally suggest you keep as few males as you can and still meet your goals. That's not because you are guaranteed problems with more males, just that problems are more likely. I don't know if the right number for you is zero or one.
Good luck and again
