I - believe - you have a decent Drone, correct? Maybe look into one that - Could - 'fly / transmit That Far', if it had to? (I know several 'Mavic Pro's should do it (even With the 'noisy terrain' / trees, etc) And, I also know Those are a $everal-K investment (and, what if it crashes, etc ) but.. Would Certainly seem a 'valid Investment', for relieving You of precious time / energy, while still performing such Important 'recon'.. Again, just a thought.
Lots more to say but this I can respond to right now. It's HIGHLY illegal to fly a drone near a fire, what is more, the fire aircraft stop flying if they find out people are flying drones near a fire.
What I did end up using a lot, was someone on the other side of the valley had a thermal webcam, and they set it up facing the fire, that site was essentially just running in my house 24/7. It was useful, but nothing beats actual eyes on the threat.