OK to have multiple media queries for each content type's CSS?
First, I'll say that I'm not sure if I should even be answering this question.  I don't think this is a Drupal specific question.  You may get more/better answers from a forum dedicated to CSS.

Having said that:

There's no reason this shouldn't work.  The CSS is valid, and if it helps you stay organized, I say go ahead.

I guess there could technically be concerns regarding the performance,  but I highly doubt you'd ever be able to see/feel a difference.