This is brilliant. I don't know what a pissed off spammer with who knows how many of your info could do, though. The last time I made one angry for wasting her time, I received even more calls from other spammers.
(1) Usually they think my name is the guy who had my phone number almost 10 years ago. I “correct” them to a fake name, but it shows their record keeping is not good enough to track anyone down.
(2) If they tried to follow through on the death threat, they’d have a hard time getting a visa with “need to kill citizen” as the justification.
Early on, I had a temporary bump in calls after doing this. If you stick with it for a few weeks, eventually you’ll get on enough “real” do-not-call lists that the calls fade away.