The in-laws often really don't have a clue what really goes on.
Here's something else I've learned, though--whether the kids are "good" and respectful and well-behaved isn't always a reflection of what kind of parenting they got. I worked as a prosecutor for 22 years and have seen kids, who were apparently very well raised by fine parents yet went completely off the rails. And I've seen kids raised under horrible conditions who turn out to be model citizens. There's no reason for either parent to take all the credit or blame for how kids turn out. Good parenting helps, bad parenting hurts, but it's more involved than that.
Katchie, I understand how you feel--seriously, I do--but I think the more secure you feel about your own life (which will come in time) the less you will stress over how people view him.