No fucking way I would do that if i were them. What if for some reason somebody goes into the house for something they need? Or what if they have hidden security cameras or a camera to see if the babysitter is hitting their kid? you never know what somebody has in their house. people, as we know, can be weird
Since they use toxics to exterminate and people are told about that explicitly, it wouldn't be too bright to go back in at night. The babyphone issue already popped up when one the guys told Walt, that he disabled one of these in the house. Shouldn't be too difficult to block/disturb any of these signals while cooking anyways. Don't think that I'd worry too much about that causing major problems.
Especially because that scenario makes them extremely mobile and unless police figures out that the extermination business is involved, it gives them the possibility to pack up and setup shop in a different place within hrs...so way easier to cover your tracks / get rid of any evidence once you get into hot waters.
The card counting seemed a bit odd, but then again if he was a problem gambler, I guess you wouldn't want him around casinos even if he was able to make money in BJ....especially since the way they told it to Hank/Marie the whole gambling thing affected his personal life, he lied to his family about it etc., so their was cause to worry/be angry.
But you're right, that if you look too deep into it, there are some weak points in the whole story, but overall this series is very well written.