Soup, how do you know your husband quit? Did he go to rehab or join NA? The vicodin on the floor is mighty suspicious to me. It sounds like you are exhausted by the what-ifs, so I hesitate to mention this, but there are some pretty clear physical signs that someone has been using opiates. Maybe one of the most reliable is that when they are high, the pupils of their eyes get very small, even when the person is in a well lit room.
Anyway, I don't think you're going crazy, it sounds like reading online just brings you closer to admitting that maybe your husband is still using, and that is a terrifying thought to you.
Maybe it's time to think about where your boundaries are regarding addiction. It might make you feel more in control. Will you live with an addict? Will you tolerate lying from a spouse? Do you feel comfortable allowing your children to live with someone who is using and dropping pills on the ground? Only you can say what you are willing to tolerate. Unfortunately, it may be very hard to get the truth from him, but if he is using, it will start to show without you having to do too much detective work. He will be out of it, money will be disappearing to feed his addiction, unless he somehow has health insurance and is getting prescriptions. It's the old "if it quacks like a duck, it's a duck" thing.