Worked as a fire fighter one summer in Florida. Most residential structures will catch fire from a vortex that gets created under the eaves or from the roof.
Best course of action is to evacuate. If you can place a sprinkler on top of your roof and on the fire side of the house, that may save the structure. I’ve seen it work before. Best to not have any flammables within minimum of 50 feet of the house. Soak the ground near the house 10 feet or so.
Most people worry about the fire and that is bad enough, but they forget about the smoke which is often the real killer. Without the right breathing masks, even if your “block” is not burned, the smoke can be bad enough to kill.
In a hot fire - not much survives. I’ve seen a crown fire move so fast that trees would first catch and then the fire was so hot that the water inside the tree would turn to steam and literately blow apart the tree.
If you can, get him out of there. Wild fire is nothing to mess with and by the time you realize you are in trouble, it is often too late.
Trust me after living in Colorado for 45 years I’m aware of what wildfires can do. We are about equally between the High Park fire in Ft collins and the new fire in Colo Spgs. My kids and I have been setting records for using our rescue inhalers for asthma. While it is highly unlikely the flames will reach his house, the smoke and general chaos can be as bad. In addition, if he were to have an unrelated medical emergency it would be very hard to get emergency care to him against all the fire traffic.
All who are near fires should evacuate even before being told they have to. That being said, what can you do with a stubborn 86 yo man? I can’t physically remove him and DH and I are working this weekend, so we cant go down and stay with him in case. I pray for all in harms way from the many fires.