Re: with my cell-phone off/ambiguity
I sense no difference between the first two, and in both cases, it seems to me that you've taken your phone with you, but it's off.
I sense no difference between the second pair, and it could be ambiguous. I had originally thought the baby was left at home, but it could be either one. I guess because it would feel more natural to say "When we left the house [taking the baby with us], the baby was asleep" that I felt the baby was left behind.
I can't say what the difference is, except it's just how I interpretted them. It's entirely possible another native speaker will draw different conclusions.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.