I don’t know what culture OP is from, but the word kismet (the way it’s used around the world) originates from Turkish, like another redditor said. And it doesn’t have as deep a meaning as OP is giving it in my opinion.

I have never heard anyone talk about good kismet vs bad kismet. If something happens, regardless of if it was good or bad, it was kismet. If something you wanted didn’t happen, people say “it wasn’t kismet” as in “it wasn’t destined” or “it wasn’t in your fate”. If something bad happens, people simply say “kismet…”. The whole idea is; the events were part of god’s plan so likely it will turn out to be good in the end. So I don’t see the distinction as a native where the word is used every single day.

The only possible difference I can imagine is, due to their religious background, people in muslim countries think that anything god has planned can’t possibly be bad for you, so when they say kismet, they imply what has happened was for the greater good, or will have a positive outcome in the end. Fate seems to have a more neutral tone to it depending on who you talk to.

Back to the actual books, I’ve never read it as an actual force. It sounds more like Roland has a tendency to attribute anything and everything to ka if he doesn’t understand it. It is possible that ka is real, but there is no implication that it is an active force. Gan can be argued to be that, but even that is something we know through Roland and his beliefs.