Do I have a negative canthal tilt + lower lid retraction? If so, what can be done to correct this? (photo)

You have mild lateral lower eyelid retraction but not gross negative canthal tilt. You can find more details on following link below. Important to understand the difference between canthoplasty and lower eyelid elevation. Skype consultation available.

Yes, it appears that you have a negative canthal tilt as well as a negative vector in your cheek region. It does not appear that you have lower lid retraction as you do not appear to have significant scleral show.

so negative cantonal tilt is the angle from the inner to the outer cants as a neutral forward gaze. You angle may be ever so slightly downward (which is more normal in males) but it is very subtle. You did have a little scleral show laterally i.e., your lower lid bows towards the lateral side. This can be corrected in a number of different ways and is often a sign of lower lid surgery. Equally it could be how you are made. Careful not to do too much to correct this though as in men it can be very feminising. 
Hope that helps, 
Adam Goodwin