(Background: similar circumstances as this question; the speaker is a sleazy low-level gangster commenting on sex workers in his employ.)
Breaking it up by sentence, here's what I've got (subject/topic marked in bold):
- 駄目な人間は、駄目なものだな -- Hypothetical/general about people on the whole.
- まったく、愛想が尽きるよ -- The speaker complains that his incredible benevolence is wasted on such human failures.
- ほかじゃ、鼻もひっかけないような大年増に、きまりの組合費だけで、シマを分けてやっているんだぜ -- ?? I think the speaker is saying, "If things were different, they'd [the sex workers would] be under some matron who'd go easy on them and only take the [mob] family cut off the top, and let 'em split the rest."
- せっせと稼いで、足を洗うことでも考えたらどうなんだい -- ?? "How about they [the sex workers] put their backs into making money and think about getting out of this [criminal] trade, huh?"
- いまさら、ヒモに可愛がってもらえるような柄かって… -- ?? "[do the sex workers actually] Think they've still got what it takes to get favors from a pimp anymore?"
5a. Alternatively, "Do I look like the kind of pimp they can squeeze favors out of?"
I'm mostly unclear on 3 and 5.
The question is, how do you know (especially for the native speakers) what the subject of the sentence is as it changes from sentence to sentence? Initially what threw me for a loop was the cascade of increasingly unclear clauses (the speaker is monologuing, which doesn't help). (I've seen this before, but never so intensely as here in the efficient prose of 阿部公房)