Monogamy is very rare among mammals, but common among some birds. Birds like swans display either monogamy or serial monogamy: having only 1 partner at a time, though not necessarily for life. Dwarves are, it seems, one of the few monogamous species. While I doubt that adultery or rape would be likely among dwarves, they should be able to remarry after a lover has died or divorce if a lover has done something horrible like murder a child in a tantrum. Serial monogamy would suit dwarves and exists in nature.
Humans are far less pleasant than dwarves and should have the whole range of patriarchy, adultery, polygamy or concubinage, double standards, rape, sex slavery and so on. This will create ethics clashes between them and dwarves which could have interesting consequences. Elves appear to be matriarchal, so their society could be one of male drones surrounding dominant queens and competing for her influence by satisfying her...
What makes violence fantastic? The presence of a goblin? The act itself is often not unknown to the average paramedic. Dwarf crushed by falling logs? That happens. Body parts pulped by a hammer? That happens too, whether by accident or not. Car accidents feature parts exploding into gore and people burned to death, and are certainly not outside the experience of an English speaking person. The only kinds of DF violence I could consider to be truly fantastic - that is, they do not really happen - are the syndromes of forgotten beasts, but even these have many of their symptoms repeated by diseases or chemicals.
In my life I have seen 2 accidents where blood was gushing everywhere in a rather DF-like way. One time, the blood was mine. I have never seen an act of sexual violence. Not so outside the frame of reference. If anything, sexual violence is more outside the frame of reference in that it is usually perpetrated by somebody who knows the victim and out of sight. It is often an invisible crime. Personally I think the kind of exceptionalism that elevates sexual violence above all the other forms of violence only helps to keep it out of sight and out of mind.
It is very relieving not to have smeeprocket around for this.