What impact does Dunstan's mother make, in her role as a woman, in Dunstan's life as he searches for meaning?
The big question I'm trying to answer is "What comment does Fifth Business make about the particular role of women in the course of Dunstan's search for meaning?" I'm generally okay with the impact of each woman (although I'll take more ideas), but I'm not sure about the part of "searches for meaning".
I guess I think of Dunstan's mother as a primarily negative influence on his "search for meaning." Mrs. Ramsay was so competent at everything, and so dominant in her family's life (and the people around her -- witness her influence on Mrs. Dempster) that Dunstan identified a close relationship with any (sane or living) woman as threatening. After Dunstan had his epic fight with his mother as a teenager he never saw her the same way again, -- he had always felt dominated and belittled by her, if in a beneficent way -- but that incident cemented his feelings of fear of her and the desire to avoid her, and, by extension, feel the same way about all women.
The polar opposite of Mrs. Ramsay was Mrs. Dempster, and it was on she, after his mother's death and his failed engagement to Diana, that Dunstan lavished all his attention. She was his "saint", or so he believed because he thought he had witnessed three miracles performed by her, but she had the unique quality of being utterly incapable of dominating or controlling Dunstan in any way. Certainly Dunstan took such tender care of Mrs Dempster partly out of guilt, and perhaps disinterested pity, and a very personal gratitude for saving his brother's life, but also a relationship with her was extremely safe for Dunstan. It was safe because Mrs. Dempster was mad, friendless, and without any family (except for the absent Paul,) and she became increasingly helpless. There was nothing that Mrs. Dempster could do to control Dunstan, except in the help he gave her willingly.
This was, essentially, Dunstan's relationship with all women until he became close to Leisl. Even though Dunstan was free of his mother after the war, because she had died in the 1918 flu epidemic, her influence followed him for most of his life. Though she had been a well-meaning person and mother, she had awakened in Dunstan a deep-seated fear and loathing of women.
This, I believe, led him to search for "meaning", at least partially, in the pursuit of hagiography. While an erudite and interesting subject, it also afforded Dunstan access to people's lives (the stories of the lives of saints), especially women's lives, without any risk of being dominated himself. So rather than performing a search for meaning through his own personal relationships Dunstan was able to dabble in the essence of humanity and divinity without any chance of being dominated or hurt himself. He was very good at hagiography, primarily because he was able to devote to it the energy and time he would have spent on other relationships (during his most productive years of writing he taught bachelor-style while living in a boys' school, carried on perfunctory sexual relationships with women he didn't love, and his only real friends were the Stauntons, to whom he felt himself to be infinitely superior). Father Blazon somewhat pulled Dunstan out of himself, and, ultimately, Leisl would complete the job, but Dunstan's mother's primary influence was to drive Dunstan away from female companionship and close personal relationships of every kind.