Blues considered a key, or is it just a scale ?

Hi, please just put some short answers for these questions...some of them are just yes or no, so you can put that for those type of questions..

If I played these blues scales over these chords, would I be playing in 3 different keys? Or would I be playing in the key of either C major or A minor?
Dmin chord- play D blues
Emin chord- play E blues
Fmaj chord- play F blues

C7, F7, G7...what key would this chord progression be in?
What blues scale would I play over each of those chords?

Would I play the A blues scale over a C maj chord and a C power chord?

Is A blues considered a key, or is it just a scale?

Would I be able to play the A melodic minor scale over an F power chord?
Over a chord that has a G# note, I probably wouldn't play the A blues scale over it, right?

Thanks,
please let me know,
Sarah