As many said before this game has some problems in the way it is designed. The NTR-path is not accessible if you aren't actively doing everything to push the girls away from you. Devon is not really doing anything to get them, he isn't a challenge nor a danger, you don't compete against him. For a game called "The guy in charge" it lacks the guy in charge.
Even if you are on the NTR-path Devons behaviour is not one of a dominant guy in charge but of a beggar who begs to get into Karens pants, and the only reason she lets him is because she is alone and he is her last straw for some action. That's not sexy at all, that is almost pathetic.
If I could give some advice:
Completely change the game mechanics. Make Devon a guy who gets control over the two girls over time, not by begging but by taking charge. If you feel like it you can add blackmail or coercion, fine, I personally like some non-con, but most important: make Devon somebody who can be taken serious in the role of the alpha.
Make the main char somebody who competes against Devon, either in a friendly way (wingman-bro-path, sharing) or in a hostile way (cuckold, cheating). If he "wins" this competetion you can have the non-NTR-path, if he "loses" you have your two NTR-paths. In either way the game mechanics should reward the effort of the player and not force him to play bad on purpose to get Devon in charge.
Usually it's a good thing to have elements of attraction and repulsion in a relationship. Hate / love if you so want. For example make the girls love Devons confidence but hate some of the things he does to them. Make them enjoy the company of the main char but let them hate what he looks like. Or whatever. I personally don't like this boring storyline of "She is falling for him because he is so nice, looks good and has a big dick", no matter if it's the mc or another.
Make it so that at least on the NTR-path, getting on the good side of the girls, being nice to them and winning their favour isn't enough to get rid of Devon nor to stop him from sleeping with them. Improving relationships should be the main drive for every path but the outcome should differ (e.g. "Yes sweetie, I like you, but Devon has forbidden me to give you a kiss, so I can't. Be glad that he makes me walk around naked and lets you have a good look at me").