Jason's father is almost an antagonist in the perspective of Jason. Billy grew up in Italy. Little is known about his childhood by Jason, however one key thing is that during his years as a child, Billy's father disappeared. To the present day, nobody knows where he went, or if he's even still alive. Because of this, it has tampered with Billy's head. Billy is a very classical, hard-working family man. However, he isn't the charming father Jason has always wanted. Billy usually tries to hide his own feelings by cracking wise-jokes or keeping an upbeat attitude. Billy often drinks beer casually. Much to Jason's disliking. Billy never gets hammered, however he often does get tipsy. 

All in all, Billy means well and is a humble person. However the way he handles things are something Jason has a problem with. Anything from a normal voice to a VERY SUBTLE Brooklyn/Italian accent would suit this role. Never have the voice too polished, as this character is meant to break the typical "honey i'm home" father trope. Play around with a scruffy voice. At the very least include one take with your normal speaking voice.