I like the idea. Yes, there's the need for both. I'm thinking about just making the text size variable according to the number of lines in the snippet - I think that makes more sense.
That's a thought, but even moderately sized snippets might get hard to read. I think this concern is especially valid because the rest of the text on the site is large and easily readable from a distance, so making the most important text–the snippet–smaller would be out of place.
Just change the layout. The 'play' button and execution results are equally logically placed under the code. That should give you enough space for snippets of any size.
Just make the area re-sizable. That way you can flick through them easily, but re-size ones you want to study.