...cannot quote text to support any disagreement. Still, I do not think Darcy was jealous of Col. Fitzwilliam. Darcy and Fitzwilliam were close, not only as relations (which implies familial obligations and loyalty) but also as co-guardians of Georgiana. If Darcy thought Fitzwilliam was attached or becoming attached to Lizzy in such a way that he would marry her and sacrifice the fortune Fitzwilliam needed to support himself as he planned, I have no doubt Darcy would have asked Fitzwilliam about it if not cautioned him about the impropriety of such as match. (I think Darcy and Fitzwilliam would respect some variant of the "guy code" about not poaching someone else's "squeeze," another reason they would talk about it if anything seemed to conflict.) In reality, I think Darcy knew his cousin well enough that he did not have to ask. So I discount jealousy of Fitzwilliam as having a role in Darcy's actions. I do not think there is enough evidence either to support or refute this idea; we are both free to speculate as we wish.

I am interest in your idea of Lizzy as an adjunct rather than as a partner in his life. I am inclined to agree with you here completely. I also agree that Darcy wanted more than an adjunct but was not sure at Rosings what that more was.