Sounds like you've got it coming from many directions. And the drake situation probably resonates so deeply for you because of your feelings about your situation with your husband.
I hope you won't mind if I make a suggestion that has nothing to do with the ducks themselves. My suggestion is that you find a way to start learning to stand up for yourself. I find it difficult to stand up for myself too, and have been through quite a lot of therapy to get to a point where I can put my foot down and do what I need for my own sanity and happiness. No one can cope when they are completely powerless--being bullied by husband, bullied by drake, bullied even by some random guy who sells you a bird. The bullying has to stop, but the only way it will is when you are ready to make it stop. For me, I had to learn that I am *worth* protecting, that I am good and strong and that I deserve to be protected and stood up for AND that I have the strength to do it for myself.
If you'd like me to stop trying to be your shrink, lol, and stick with the topic at hand, then I will say this: Remove the drake and shut him in a pen by himself. Don't put any hens in with him. Tell the person who gave you the drake that he may either have the drake back or he can wait until you are ready to give him eggs. Ignore the drake's protests and apparent attempts to hurt himself. Remember that he is doing this to himself--it is not your problem if he gets hurt. Don't worry about what the guy who gave him to you will say--he can take the drake back if he doesn't like your methods. Frankly, I don't like *his* methods--I've had hens bullied to death before I knew what to do about it, so you are quite right to be concerned.
After a week or so of having the drake separate, introduce him to the hens again. I find that taking aggressive drakes down a notch or two often calms them enough that they can get along. If he continues his bullying behavior, you separate him again for a day, then back with the girls. Lather, rinse, repeat. I suspect that he is still grieving his lost partner and once he's had a chance to adjust and sees that he's not going to be permitted to bully the girls, then he will settle down and enjoy his good luck.