In my paperback edition, this passage is on p 129, column 3.
What I think this is talking about is the consequences of her father’s being such a nice guy: his niceness had a downside in the past (keeping him stuck in his previous marriage), but is now a perfectly good thing (at the time of his conversation with Tugumi on the beach), now that everything has worked out.
Piece by piece (with very loose translations):
He was a nice guy.
Before, his niceness was a thing that caused him various disadvantages in his life (by keeping him stuck in his first marriage)．
足止めを食わせた = past causative form of
足止めを食う（あしどめをくう）(exp) to be stranded, to be forced to stay, to be obliged to stay
Seeing him at peace
like the mountains shining in the sun,
he looked calm and and cheerful.
in a situation where things had settled down as they were supposed to
manifesting the effect of (his niceness)
seeing it like this, it (his niceness) seemed very perfect and good.
Thanks so much for the detailed explanation. It really helps to get even one passage clear in my head to anchor the rest.
I struggled quite a bit with the dialogue between Tugumi and Maria’s father. Though I think some of that is that her tone appears more abrupt that I would expect, but I think that’s just part of Tugumi’s nature.
I was amused on the final page, given the general lack of furigana, to find it present on the word 黄昏 (given our previous book was Spy Family)!