I think if Reira and Takumi stay together, they might be exactly like Ren and Nana O, self-destructive relationship! since none of them has what it takes to build a happy family. Let's me imagine the scenario, uhm, how about this?
Takumi: Tadaima ( tired)
Reira: ( crying) Takumi, you were with other women right? you selfish man, you don't care about me at all ( blah blah blah...)
Takumi: I'm tired and if u gonna have unreasonable jealousy like this all the time, we cannot be together!
Reira:...I know you are tired of me anyway...
...............
err. why am I doing? lol
anyway, back to the main topic: Takumi. He might be the worst husband one can ask for but he is undeniably a good dad, he redeems himself a bit in this part
I think a Nobu- Hachi ending is possible, but in that case, Takumi will be the one who voice divorce first, he might decide to be an angel after all his evil deeds and decide to step aside thinking of Hachi's happiness
P/S:
Do u guys notice? Miu is there for Yasu but Yuri is not for Nobu, I don't think Aizawa forgot to include her in recent chapters, which mean she gonna be out of the picture in the future ( yay ^^) she is not there for Nobu in his hardest time, not qualified to be good wife