The more domestic and subservient mamano would be your best choice. Ones like the Kikimora, Inari, shirohebi, kobold, holstaur, Apsara, mermaid, Yeti, and sea bishop.
Pretty much what Aura said. As a rule, Mamono conform to their husband's tastes, though like you stated Hellhounds and Manticores lean towards the S&M side. But even then, their number one priority is their husband's happiness, so they'll do whatever they can to make him happy.
For gentle fendom, I would say:
-Lamia.
-Wurm.
-Wyvern.
-Dragon (dominant; becomes submissive if the husband is stronger...).
-Arachne.
-Nereid.
-Kraken.
-Scylla.
-Mershark.
-Giant Ant.
-Honey Bee.
-Black Harpy.
-Harpy in heat.
-Werewolf.
-Anubis.
-Grizzly in heat.
-Large Mouse.
-Devil Bug.
-Queen Slime.
...and others...
All of those capture their husbands, rape them and keep then prisioners until subverting their will, but none of then torture, beat, hurt or humilliate their man...
The Wyvern sounds fun you can ride her while you ride her also I really like the werewolf but the whole pack side is a let down.Â
Galeah, I'm going to have to disagree with some on your list. I would not call the lamia, scylla, or wurm gentle. They're more demanding of affection than they are submissive.
The Scylla and maybe the Lamia could work, but I don't really see the Wurm. She's usually a little airheaded for that.
The Lamia stalks and captures a man, rapes him, coiling around him if he tries to struggle, and never lets him go. She can become a loving wife, eventually, but only once she is sure the man has accepted his fate... before that, there is a long, long period of reverse rape and femdom.
Hence, she fits "gentle fendom" perfectly...
As for the Wurm,yes, she is tameable, but until her husband realizes that a relationship with her is like a mix between being rolled over by a locomotive and raped by Moby Dick...
For husbands who still haven't managed to tame her, she would behave like an hyperdominant rape beast half of the time, and like a clingy kid the other half of the time...