I agree. Personally, I see the “Is Frank Becca's father?” point more under the light: he's at least more likely than Trevor, for whom the time frame absolutely doesn't add up. Other than that, I personally don't really care and your last sentence sums it up well.
Another topic: What would you guys like Single Again to cover that is not sex-specific? For me it would be, in no specific order:
Abby meeting her half-siblings at least once. However, without the father present and thus only Abby, Frank, the 3 kids and their mother present.
Lilly confronting her father and giving him a piece of her mind. Yes, Abby had that too, but the trauma from her father was a formative event for Lilly for a long time and even though she's over it, I think it would be good for her.
Frank talking to Vanessa about the death of his wife. It's obvious that he's still suffering from what happened and he's never had time to work through it with little Abby because she needed him at the time.