So many pages to argue about why the MC will or won't get to lvl 4 soon...
You people seem to forget the obvious "power fantasy" coding of the story. Even when the MC trips up, it never lasts long, and he quickly becomes are powerhouse against his opponent of the time.
And it's never been more true than his fight against Monster-Deryl. He went from struggling against "Chimera-Deryl" to trashing "Evolved Chimera-Deryl" with, comparatively, quite an easier time.
He's also the first superhuman to have powers from two different lines. Ella has one of the same parents but didn't get the memory powers herself (which is why revealing that to her is a bad idea and leads to a bad end).
It's abundantly clear that he's meant to quickly climb the ranks.
While his powers are quite clearly defined, his concept as a character is "adaptibility". He faces a situation, gets a rough time, learns, adapts, overcome. Every single time with a lot of efficacy, given how deep in shit he can be at first (such as with Jake).
I'd be really surprised, given the story shaping up, if he doesn't end up level 5. Hell, actually, I think there are good chances he either gets to level 5 on his own, or if using the serum, somehow transcends the classification and becomes the first to go above the level 5.