You should be in "lockdown" - which is just a short way of saying... stop rotating, they got three days left.
Your humidity should be up in this time period. Add more water. I assume you are using a styrofoam incubator... there should be a "water tray". You should have had water in the center water compartment, now is the time to add water to the second water compartment as well.
Yes, the chicks are generating their own heat... which brings the temp up. Yes, the room temp (and outside humidity) effects the incubator.
Tempature can go up and down by a couple degrees and not be a issue. It's when it is 3 or more degrees off should you make very small adjustments.
Take those babies off rotation. Add water to bring the humidity up to 70-80%. Sit, wait, watch. Don't touch! They will be here. Just trust the process. I know it is hard when it is your first time! Good luck!!
PS. you probrably don't need another incubator. Mine has jumped up right now (they are due on Wed.) - tempature outside jumped up, so so did the incubator. No worries. Just correct and trust.