After looking at the context, I see that the situation is this:
The woman whom the son took as a wife was an indigent, and a relative of his (cognata). Now the father here speaking, is saying that her being a relative was no compelling reason to "have" her (i.e. to take her as a wife); they should have done what the law commands and given her a dowry, and she should have sought for another husband. Why was the son, instead of doing this, leading the indigent woman home (as a wife, i.e. marrying her)?
The imperfect subjunctives are past jussive subjunctives (I don't know if this is the official usual term, but that's basically what it is), not present unreal.
Perhaps Cinefactus already knew all this and was only wondering about the imperfect in ducebat.
I can't really tell you why ducebat is used rather than duxit. You know, sometimes, two or more constructions are possible and you choose the one that pleases you best in its nuance (or, as the case may be, in how it scans). There is definitely a difference in point of view between ducebat and duxit. The author chose the former even though the latter wouldn't have been incorrect. I suppose it may be that there is a conative nuance to ducebat here, but the son apparently did marry the woman (he didn't just try), so if it were so I guess it would be like "did his utmost to marry her" (and succeeded), but I'm not sure it is. It could still be a "simple" imperfect.