How can I figure out how many degrees I need to be rotated in nasal tip revision?

You should not worry so much about how many degrees of rotation you need. During a consultation with an experienced revision rhinoplasty surgeon, you will have photo imaging done. The imaging process will help you and your surgeon decide how much rotation and projection looks best for you. 

First, I'm sorry about your experience with your initial rhinoplasty. As far as the specific angles to rotate the nose to achieve an aestheticly pleasing result, that will be a discussion with your surgeon. In general, the 'optimal' female nasolabial angle should be around 105-110 degrees. This will vary based on your height, facial shape, ethnicity, and other factors. I would just suggest sitting down with a revision rhinoplasty surgeon who can use the computer imaging to estimate the correction needed. Best of luck

It is not your job to know how much rotation is necessary.  My suggestion is to have a consultation or two and discuss your concerns.  An experienced Facial Plastic or  plastic surgeon will be able to tell you how much rotation would be beneficial.  You can also have telephone consultations.  See below for exact photos to send for consult.