I just want to point out that using "massive low wattage lasers" to melt cities is pretty much the opposite of what you want to do. You either need a tightly focused low wattage laser, or a less focused high wattage laser. (I'm assuming the "massive" refers to how focused the laser is, otherwise that statement is just an oxymoron)
Also, if you assume that sending you back splits off a new timeline, what's the point? You can't change anything if the changes only take effect in the new timeline. (I will note that I personally favour the Copenhagen interpretation of Quantum Physics over the Many Worlds interpretation, but you seem to indicate that the latter is correct)