Valid critiques of Cas12a2 must acknowledge the mechanistic differences between Cas9 and Cas12a2. There is no research to suggest Cas12a2 is "sloppy" and significant research that demonstrates it is not "sloppy."
I appreciate the skepticism but I would encourage you to study the actual mechanism discussed in the paper.
You don't. Healthy cells will also get these nanoparticles, but without the triggering DNA sequence, the mRNA payload will remain inert and eventually will be degraded.
This is my understanding as well.