portfolio questions

I have two questions concerning my portfolio. Here is a link to it:
http://www.mkillustrations.com/index.php/portfolio-2/
First question is about the featured images that create the thumbnails on the portfolio. If you look at the thumbnails then at the actual image (when you click on it and it becomes larger) you will see that the image is being stretched horizontally. Is there a way to make this not happen?
Second question is about the larger images. I’d like to be able to have arrows that you can scroll through the images when they are big. I thought this was accomplished by checking the box when you set up the portfolio page that says, link this to previous and next projects (i’m paraphrasing). But I have it checked on all five of the portfolio items and the arrows aren’t there to click to the next imaage. Am I doing this wrong?
Thank you in advance.
MK