Probably too late, but I decided to give this a try today and came across your post. I had only one issue - I had to use POST instead of GET. Other than that, everything seems to be working well. Not sure if you still need help, but I've attached some screenshots in case someone else faces similar troubles in the future.
Here are the variables:
Actions:
For the two types of actions, the set variable I create one per data
This is my post:
This is my spreadsheet 
I decided to send a new row every time one of the variables changed, instead by time. If I'm happy with the results, I may create a script to remove or collapse the data into a new spreadsheet with an average per hour or something, so I can control the number of rows.
Lastly, I'm not sure if it was mentioned in the original post, but it's very simple to share this in your dashboard by publishing the graph and using IFrameAdvanced.
PS: in your post, looks like you are accessing a device that has no value temperature. Maybe that property has no valid value. Check in the device what value has this property. For your screenshots, the values are null
