You may have a list in your CV with "submitted manuscripts", yes. Only change the list if you get accepted, or your submitted manuscript is rejected (by striking out all the info on the now rejected item.
Yes, you should include the papers under review and in preparation, in two separate categories. This is standard practice and it helps to show your research stream to search committees in case you apply to an academic job with the CV.
It is better if you list only the published papers in your CV. But some people list papers under review also in their CV's. If you are listing papers under review in your CV, clearly state that those papers are under review and state them separately.
Sure, I don't see why not. In fact, I do it myself.. It gives an indication to potential employers that you're active in your respected field, even if the articles have not yet been published.