His etudes are generally marked to be played very fast but have a simple structure. I believe that one can have as a final goal to play them in the indicated speed while very few people actually can do that.
If you take the first lesson as an example where a half-note is to be played 108 (b=216 as you say), playing 16:ths in that speed means that you need to hit 216/60*4 keys/second = 14.4 /keys per second.
While Czerny's lessons can be a great improvement to achieve speed, they can be terrible frustrating and can even do harm unless you do it right. Never feel tensed but rather focus on playing them correct but slow and speed will come naturally. It is not for certain that you ever will be able to play them in speed but I think (if you are inspired) you should continue try them out. I also believe that you should consult a teacher to help you approach them.
Remember, Czerny was Liszt's first "real" teacher so the exercises cannot be terrible wrong