I will try and answer all your questions as best I can.
As far as grades go, you must maintain a "B" average and the grading scale is 92+ = A, 82-91 = B. You must make a B or better in most of the coursework, specifically anesthesia related courses, there are a few classes you can make a C in, but I wouldn't recommend it.
My class started out with 18, and we lost a couple at various points for them not making a B in an anesthesia class. They both sat out until the class was re-taught and have now started clinical portions. I cannot remember all the details related to grades, probation, etc.
As far as clinicals go, they are pass or fail and are based on your performance in the clinic which is evaluated by your preceptors. We had a list of "milestones" that had to be completed at various stages of our clinical experience. I had no trouble in accomplishing the milestones.
During the didactic portion of our program we were in class most days of the week and spent as much time studying. If I remember correctly we had a couple of quarters with one off day per week. After 12 full months in the classroom you begin clinicals 3 days a week for the first few weeks, with the other 2 days in the classroom. Then you attend clinicals 5 days a week, with one half day for an afternoon "seminar" class. The teaching portion plays a very important part in laying a foundation for your clinical experience. Early on we spent time in the lab working with the anesthesia machine. They now have more tools to teach insertion of invasive lines, etc.
As far as strugglers go, there are not many of those in anesthesia school. But at Samford, the staff is very willing to help explain concepts and work with you. It is very important to have a great study group, without my study group, I wouldn't have made it! Each instructor brings something to the table. One may be more theory oriented, while another is more "this is what you are really going to see".
You really need to shadow a CRNA for a day to see what it is really like, as far as the clinical area. I am not at Cullman, but have had several classmates spend time there and loved it.
I hope all this helps. Feel free to ask more if you need to.