Okay, based on your estimates, I would wait until Tuesday to poke holes. If you do it, you'll be looking for movement under the membrane, and/or a little nose (bill) sticking into the air cell. You can see this by candling if you have experience, but when you're not sure based on candling, then poking a hole may be your next step. Anyway, when you poke a hole and shine a light in, it will be very obvious if the duckling is alive. If it is, it will at least be breathing, and you can see that (unless it hasn't pipped internally, in which case you'll see it moving against the membrane).
If it's alive, whether you help or not will depend a lot on the circumstances. If it looks like it's trying to poke through the membrane but the membrane (I'm talking about the part that is covering the duck, not the part that is attached to the shell of the air cell) looks white and dried-out, the duckling may be stuck, and you can help by tearing the membrane a bit... but I think when/if you reach that stage, you'll want to come back for more specific advice... because there are just so many variables.
Good luck--sorry it's so stressful--wish I could at least loan you a reliable incubator so you wouldn't have to be up all night monitoring.