Gonna try not to power level too hard or get too MATI, but after reading those messages between Gator and May...girl, run, don't walk. I've seen this before, and you are in deep.
I knew a family where the dad was just like what May's describing. Specifically the desire to always be in control. More than the substance abuse, more than the short temper, it's the desire to always be in control that will really ignite this situation if May ever tries to leave. Especially when you consider how little control Ralph seems to have over everything else in his life, which always make control freaks exert all the more pressure on the things they do still control.
If May's pregnancy is still viable (big

energy, I know), she owes it to her child to get the fuck outta dodge. I vaguely remember hearing something about May being abused as a child, so if that's what's causing her to drag her feet on running back to her parents, fair enough, though she seems to be on good enough terms with them to meet them for holidays and funerals. Even if she doesn't want to go back to her parents, she has numerous options in terms of organizations that can protect her the moment she picks up the phone. There's no excuse not to act here.
Whatever difficulties you have with your family, May, I can
guarantee you that not a single one of them is more important than making sure you and your (possibly fake) child are safe. They would much rather see you and their granddaughter secure than have to drive down to Virginia to identify your body after the Gunt disposes of you in an Arby's dumpster. If this situation ends up the way that even Ray Charles' desiccated corpse knows that it's going, Ralph will reach for the first thing he can get his hooves on to control you once you step out of line, and that might mean your child.
The best time to dump the Gunt was the moment he traded tummy slaps with your ex's tranny friends. The second best time is now.