I think you are reading way too much into this relationship, and probably drawing in elements of relationships from the present time into completely inappropriate contexts. Of course, the journey of Darcy and Lizzie from their initial states of pride and prejudice respectively is what occupies the action of the novel. We are shown how their "clashes" result in their humbling and character development, making them fit partners for each other. However, at the end of the novel we are shown with two characters who are perfectly suited for each other, and I think there is no sense that we can say there is a destructive element in their relationship because of its apparent perfection. They are shown to be good counter-balances for each other--Darcy's solemnity for Lizzie's sense of humour--and we are presented with a happy ending for them as they grow old together.