. . . first, it should be understood that Henry Crawford gives me the creeps. That said, here is the reponse to your question.

Yes, Henry (and all of us) should be held responsible for his actions. Although I would love to be able to discuss this with Jane Austen, I cannot. However, from all that she has written, I believe she would agree with me regarding human responsibility.

Henry, affianced or not, married or not, is reponsible for Henry's actions. The only thing that would let him off the hook would be someone slipping him the male equivalent of the date r**e drug, mental deficiency, or, maybe hypnotising him . . .

It was his decision to attempt turning Mrs. Rushworth into Maria Bertram. It was his decision to let her accompany him once they'd had their horizontal tango. He could have remained on his estate, helping the poor tenants. He could have gone up to London and lived like a monk. He could have found himself accidentally in the company of Mrs. Rushworth, excused himself pleading a family emergency (or whatever) then fled the premises. He could have done all of this . . . but he didn't.

Anyone who would try to make Fanny responsible for Henry Crawford's actions is trying the logic equivalent of attempting to make the sun rise in the west. 'T'ain't possible. These poor souls (the characters in MP who blame Fanny) are delusional. Mary Crawford because she loves her brother and would prefer not to examine his profligate ways too closely. Mrs. Norris because she hates Fanny and loves Maria.

Did Henry truly love Fanny? It is possible. I now realise that his actions at Evringham remind me of that scene in the film "Dangerous Liaisons" when Valmont pays his servant to find a wretched farm family so that Valmont can be spied upon while helping them, thereby favourably impressing Mme. deTourvel.