Did Willoughby love Marianne?

I did not then know what it was to love. But have I ever known it? -- Well may it be doubted; for, had I really loved, could I have sacrificed my feelings to vanity, to avarice? -- or, what is more, could I have sacrificed hers?

In Ch. 44 Willoughby says (above) it may be doubted that he has ever loved and that he must not have loved Marianne because he sacrificed their feelings for each other to his greed. All the affection that he admits for Marianne is that of being “sincerely fond of her” which does not seem equal to his behavior at Barton. Willoughby also asks Elinor: “Tell her [Marianne] of my misery and my penitence, tell her that my heart was never inconstant to her, and if you will, that at this moment she is dearer to me than ever". Willoughby’s heart was inconstant to Marianne—he cared much more about himself and materialism than her.

What were Willoughby’s intentions towards Marianne?

Willoughby planned to fix his money problems by marrying a woman of fortune and told Elinor “To attach myself to your sister, therefore, was not a thing to be thought of” but his vanity was “elevated” by Marianne’s “lovely person and interesting manners” and so decided to play a game with her. He did all in his power to please her which apparently includes misleading her about his tastes, opinions and enthusiasms (Ch. 10) but worse his intention was to gain her affection just for the fun of it:

“Careless of her happiness, thinking only of my own amusement, giving way to feelings which I had always been too much in the habit of indulging, I endeavoured, by every means in my power, to make myself pleasing to her, without any design of returning her affection."

Willoughby knew his behavior had bound him in honor to Marianne but just could not bring himself to it. He described himself as “scrupling to engage my faith where my honour was already bound” because of his financial situation. Then someone exposed his affair with Eliza to Mrs. Smith causing a breach between them. He then abandoned Marianne without the guts to say he was not coming back. Willoughby’s resolve to marry her really only lived for a few hours before it died in his fear of living a less exalted lifestyle:

But in the interim -- in the interim of the very few hours that were to pass, before I could have an opportunity of speaking with her in private -- a circumstance occurred -- an unlucky circumstance, to ruin all my resolution, and with it all my comfort.