Tbh I never experienced something like you are describing, sounds to me like there's a cable touching the blades which makes the noise but I assume that's not it.
50 degrees celsius is perfectly fine for a CPU, danger zone is somwhere around high 80s/90+, but it will shut itself down if it overheats so you'd notice. Fans definitely shouldn't die that fast tho, maybe you just got unlucky?
As long as you sing the notes correctly it won't sound terrible, it doesn't matter if your voice doesn't sound good as long as the content is good . Keep it up man! (or just throw some autotune in there)