Is this circuit safe? What happens when something goes wrong and the load becomes a dead short?
Define safe. lol. For all it's worth, this circuit isn't worth the risk of injury one might suffer if something goes wrong. If you want a cheap and accurate watt meter just buy the "kill-a-watt" its only about 20 bucks.
For my project, I needed to figure out how much wattage a device was using. This was a crude way to do it but it worked for my specifications. I guess a fuse would be a smart addition to this circuit.