I have used that foam.... to fix a fence post :B
The only issue I see is that you are stuck with a full bag even if you need only half.
On a long pour I would have suggested a bit shorter mix and start pouring quickly but you probably have the hang of it now. Yes it gets hot enough to burn your hands. I used latex gloves for easy removal. Let it cool before you trim the excess.
I have two more posts to fix next month. Will do two posts with one bag this time.
After seeing the videos looks like you could have done one or two spots with the bag. Easy to cut away excess after it cools and hardens a bit.