I would like to know what does mean exactly "like" or "been like" in this sentence: 'I've tried to understand what's been like for you, having gone to war, having lost your arm, not having married or had children'

And too the mean of this 'so be it' in the following sentence: 'It was perhaps not the way in which his father would proceed, but so be it: he was not his father'

Thanks, jo.
I'd say:
"I 've tried to understand what you've felt, what your experience about going to war etc... is".
so be it in this sentence: "as it is/was", +/- "in fact"
This is only my opinion...
There's something wrong in the first sentence. It should be, "I've tried to understand what it's been like for you, ...".

"to understand what it has been like for you" = "to understand how it has been for you" = "to understand how you have managed" = '"to imagine how it would have been to be in your place" = "to imagine how I would feel if I had been in your place"

"but so be it" = "but let it be so" = "but let it be like that" = "but that was just the way things were" = "but there was nothing that could be done about it; it was just the way things were"

(The equal signs are to show approximate, not exact, meanings, of course.)