Alright, time to answer some questions again. Why? Well, I like to leave things clear.
Question 1- When Will the MC learn how to control his power?
Answer = The first volume of the novel. The New World volume, will deal with the psychological aspects our MC is going through, which include but are not limited to, trauma, depression, and fear.
With the MC learning to accept these things, in order to overcome them.
This arc also introduces certain changes in the world, introducing plot points for later development.
Question 2- How long will this volume be?
Answer = Not long at all. The Webnovel release is 21 chapters away from this arc ending. Meaning at chapter 40 the volume ends, as the other begins.
Question 3- Why hasn't the MC used his voice?
Answer = Fear of hurting others. And by others I mean, innocents. But mainly, the fear of losing control, right now his voice, his powers fluctuate like hormones, because he's a teenager, a crack in his voice could result in unimaginable results.
Nevertheless, his voice is yet to reach full power. The Original Black Bolt has shattered the veils between dimensions.
As for the fork. He will in the following arc work on something like that, but slightly different, a device to weaken his powers according to specific settings he will configure himself.
Question 3 - What's the following volume?
The title it's called the team. This volume will be short, and it will mostly revolve around the first season of Young Justice.
Question 4 - Love interest, when?
The love interest it's already in my patrrreon, however, the MC will attract some unwanted attention from some questionable sources, female sources before anyone begins to jump into the rope.
I hope this answers some of your questions.