I see last night as putting a damper on the 'Kat is gone' theory. Phil lies, but the idea that Kat hates her retail jobs, is apparently miserable, and is demoralized after losing out on opportunities to pivot to clerical work - that's all beyond his scope. He's become so removed from other people and the concept of empathy that I really don't think he could concoct that story unless he had witnessed it firsthand from Kat.
Now where this does highlight the lie is his constant claims that they're happy and content with their lives. Kat is clearly not and is open about that. Regardless of their personal state, she loathes the soul crushing retail work and is apparently urgently seeking a way out. So the problem with Phil's lies about their happiness is that he's, at best, speaking for himself alone, and likely also trying to convince Kat as well so that things can stay familiar and comfortable.
The stream last night seems to support the speculation that the likely issue is that Phil simply does not want the status quo to change. He probably controls the 'house' finances and Kat gets to spend her own money. He doesn't particularly care how she comes by that money as long as he has her as a trophy and a crutch for mom duties, and as long as he can burn a fortune on his various vices without her asking questions, he's perfectly happy to maintain a holding pattern. Kat is not, so while he listens to her frustrations, he doesn't want anything to happen outside of Kat basically moving to the same kind of job.
The path forward is that he would curb his spending in order to help her, and she would go into some kind of training so that she could get a better job and be content. This doesn't benefit Phil because he would have to give up comforts, and with their current arrangement, Kat getting more money doesn't do anything for him. Phil probably figured he has already 'nipped this in the butt', having learned from Leanna. Leanna started working and then wanted more and then left him because he refused to do anything for her. This time, he married Kat quickly, before she got restless, and now she can't leave him, so he doesn't really care if she has to keep working at Kroger.