From what I understand, Eric is the counter mechanic that we need to deal with it. I agree that the fact that he can just start going into Alice's bedroom with 0% Influence is bad, but that is something that can be changed in the future.
For me Eric should start with 100% on Mom, 25% on Alice (because money) and 10% on Lisa. At 20% on Alice, she will allow him buy her lingerie, at 30% she will show herself without a bra and on 40% she will show herself without panties, leading into the Massage, at 60% she will exchange "favors" with him for stuff, up until it gets to 80% where he fucks her and at 100% he has full dominance on her. Same with Lisa. It should be very hard for you to stop him from attacking all 3 of them, but that's where Kira comes in, she will help you reduce Erics influence on your family, by increasing your own. Seems a very interesting mechanic, if he decides to go that route.