Another thing that speaks against Tsukune's powers going out of control, is the fact that Moka needs to keep her composure, if she wants to successfully suppress her Shinso powers, since as we know high emotional outbursts are also capable of awakening the power of an Shinso.
Now, do you think that Inner Moka would be capable of keeping her composure, if she sees how Tsukune's berserk form currently looks like, especially after chapter 54, which in my opinion showed that Inner Moka's composure is pretty low at the moment (which, shouldn't come as a surprise, considering everything that has happened to her, in the current arc).
Not to mention the fact that there are still a lot of emotional moments ahead of her, once she starts realizing how much Tsukune has sacrificed ... for her sake.
After all, I doubt that she realizes how much Tsukune has changed( although she got the first hint that Tsukune has changed, due to the speed, and attitude he demonstrated in chapter 54) , during the one month that they have spent being apart from each other - and once Inner Moka becomes aware of the changes that Tsukune underwent
for her sake. I believe that we will get a quite emotional reaction from Inner Moka as well (which, is most likely going to cause Akua to become even more mentally broken
)