Well seems somewhat logical for him to be submissive at this point and not turn the tables. He started out cheating on Aki by getting a blowjob and getting his penis enlarged. Now he continues to chase that high and with Aki signing off Jake doing this thing as long as she gets to do her stuff with Nichole, they pretty much amp each other into the cheating/cuck fetish. Imagine getting all the sexual stimulation you can wish for by simply following the lead. If he's mentally predispositioned for this he won't fight it. Aki being pregnant does seem like a catalyst for them to drift apart rather than him "renconquering" Aki. I can totally see him running back to his mistress and Gideon for coping with more sexual relief.
While true that he has that going for him, including him cumming from thinking about his mistress banging someone else, he's also quite possessive of Aki, as he's stated in the past that he's ok with her being with other women, but not men. Aki as well, as she stated he better not be knocking up any of the maids, she's still very much attached to him. Even if she's turned on by cheating on her husband, the sheer guilt she feels about betraying him makes me think things won't end with seperation. In my mind there are only 3 ways this will resolve while still being consistant with what's has been established by the story so far:
1. What I personally hope for, this will be the spark in Jake that ignites the more dominant and aggressive side of his new futa identity (for as established by this story, these are futa inherent traits), being pushed by his new mixing hormones to being more in charge. There are multiple scenes where Aki says something about Jake kind of reminds her of the new feeling Nicole instilled but not being quite as strong, I could see her going back around to him as Jake progresses with his transformation. In fact, now that I think about it, I'm starting to think the "training" Madame is putting Jake through might be similar to Gideon's training based on the tidbits the story has given us so far. This combined with the established ability of their being twins with 2 different fathers makes me think he'll end up impregnating Aki as well to balance things out, maybe even having his child be the first born. Hell if they could make this happen, it could let Aki continue lying to Jake as she could convince him BOTH children are his, which would probably consume her with guilt as she's shown to feel worse and worse about her lying, but it's possible.
2. Aki and Jake end their relationship and go be with there new lovers. Aki go on to be Nicole's concubine, and Jake becomes Madame's new Futa plaything. This seems like a rather large stretch given what we've seen so far. While they may be fighting a bit more lately, Aki and Jake still seem to love eachother, even if they're spending time with others, they still come home to eachother and share a bed.
3. This new level of cheating will cause him to orgasm himself unconscious, and he'll wake up telling her how great it is that she's having someone elses baby. To me it feels so lazy and while possible, would mean the writer established tons of rules and lore for Nicole and her friends, but chooses dilberately to exclude Jake. Option 3 just doesn't make sense.
According to the dev, this is a 10 chapter game and we just finished chapter 6, so we're more than halfway through the story. This wouldn't be a good time start changing the rules that have been established, as putting in some "writers convinces's" to make things make sense never really sit well with an audiance. Regardless, we'll just have to wait and see where this goes.