I think Nick's whole thing with April was just wanting to try to hurt Aaron for him getting way too close to all he has in this world which is loyal Kayla.
I agree with most of what you said except this right here. Kayla is Nick's same-old same-old, and he knows she won't leave due to financial straits. Kayla is more inertia than loyalty. Toss some chicken tendies, thc gummies, and Star Trek dvds in her cage, and she's relatively content. She may complain once in a while, but as long as she's suitably drugged and left to her petty comforts, she won't leave. I'm sure there's been many an evening that Nick has wished she would, leaving him free to drink, drug, and pursue both fame and chlamydia in LA as a child-free bachelor comedian.
April was supposed to be a simple bit of strange, which is why Nick was willing to do a temp trade with Aaron. Nick didn't expect that bit o strange to be so, so addictive. He was stuck to her as firmly as a middle school boy is stuck to his first cum sock. He fell for her harder than Russ Greer falls for a hooker at Olive Garden. April consumed his thoughts, and Kayla, his children, and especially the dog were barely an afterthought.
Nor did Nick expect Kayla to warm so much under AA-Ron's sweaty caresses. Nick would have been satisfied with sharing April's fishy affections (and offloading the expense of her care and feeding) with AA-Ron if it hadn't been for Kayla's mysterious snow-angelic sexual awakening. Nick probably mistook Kayla's previous sexual disinterest in
him for frigidity. As soon as he realized that Kayla and AA-Ron were catching feelings, he started doing everything he could to sabotage that part, while still holding onto April as punishment. And his plan totally would have worked if it hadn't been for those pesky hungry smelly kids, a bunch of Scandinavian prudes, and some autistic nerds on a flightless bird enthusiast site.
