As for the screen, I think it probably depends on what sort of screen system they have. On my house, it would be easier to use a butter knife or the corner of a credit card to pop one side of the screen loose, then the whole thing would come out silently.. There are these little sliding doo-dads that are supposed to hold the screens in place but they don't work real well. So long as you apply pressure several inches away from the doo-dad, the screen will pop right out.
So with our screens, cutting would actually be noisier.
Whoever removed the screen may not have used that window as an entrance/exit point. They may have been preparing for a quick exit if someone woke up.
I thought the window itself was open. I'll have to go back through the links to see.
I think if Isabel had started making a lot of noise, the abductor would have ditched her and run. But many small children are used to being moved in their sleep by their parents. So long as they are picked up gently and held securely, the child just stays asleep.
In the Sierra LaMar case, there have been news stories about attempted abductions in the general area. Each time, the wannabe abductor was foiled by relatively simple means: the victim screamed or started running and the abductor took off. That says to me that it is likely that abductors make many tries until they find a compliant victim. A little girl who stayed asleep when picked up would be an ideal compliant victim.
To me, the dogs are a non-problem. I'd just fill my pockets with a good treat like garlic roasted chicken cut into bits and the vast majority of dogs would instantly be my best friend forever. Very, very few owners go to through the time and effort required to teach a dog to refuse food offered by a stranger or food on the ground. I teach my dogs to refuse food on the ground but I'm a dog trainer and weird, so I don't count.
I realise that TPD seems to be doing all they can to shine the spotlight on the family while they employ plausible deniability but I'm just not convinced yet.