"It is enough!"
What about "Det er nok"? Can it be used in the same situations (well, apart from the rope/marriage fight situation because I kind of see how it might be different)?
I think it becomes a more pronounced "that's enough/enough of that". For my 2 bullet point I'd say "Nå er det nok" (actually it's better off screamed). And for 1 "Det er nok nå". It need the "nå" for those.
But as a neutral term it will do OK as an alternative, maybe even more in the meaning of "it will suffice".
it's holder sort of like "suffices" or is there no real english equivalent
No short answer from me. Ever.
Someone is topping up your cup of coffee and now you think you have enough, so you quickly (but rather politely) stop them by saying det holder. It is enough, that'll do, I don't need any more. Or, you are making a presentation and think it lacks some arguments or maybe a fancy diagram, but your colleague assures you you will be fine. Det holder. It is enough, you don't need any more.
Your kids are yelling at each other and you are really fed up and want them to be quiet to hear them out one at the time, so if one is interrupting you will tell him/her det holder. Enough of that, I'll hear you later.
You are climbing a rope and feel somewhat insecure, it looks a bit frayed. But you are reassured by the instructor, det holder. It will hold (your weight just fine). Or someone asks about your marriage, you guys were in a ugly fight last time he saw you, det holder. It will hold (we are not leaving each other. Now.).
I think the first one was what they set up for really:) It is a common and polite phrase around foods and drinks.