Nope. There's no way a handjob can be construed as a rape, even if Frank was drugged and tied to the bed (or the shower wall, lol). You might argue sexual harassment, sure, or even maybe sexual assault (I mean, what Abby is doing has strong overtones of harassment, for example, and I guess the way Lilly throws herself at Frank the first time could be construed as sexual assault if you were to dismiss all context), but rape means penetrative sex. Frank can't be "raped" if Becca just touches his dick.it is already rape as soon as its against the victems will. there has to be no threat.
Also, if it were really against his will, he would have put a stop to it--nothing prevented him to. But he didn't. Because subconsciously, that's what he desires (and he actually admits it to himself, although he's still in "I can't, she's my daughter" mode).