I find that using "By the time" stresses the length of time in the situation, whereas "When" is more for general usage. I.e. "When I get home, she will be sleeping" - This is a simple fact. "By the time I get home, she will be sleeping" - The use of "By the time" here stresses that it is going to take you an amount of time to get home. (a) "When I got home, my family had already eaten" Vs. (b) "By the time I got home, my family had already eaten". My interpretation of (b) Would be that something happened to delay your trip home (maybe traffic? Who knows...) - but it definitely implies that something delayed your time. It's a very minor difference, but a difference nonetheless.

You're right, they're pretty much the same in meaning.

Hello! "By the time" means before, so in the sentences with "by the time" the meaning are before to get home.