You've about hit time all, also there is the Sheldon museum Miller museum, and Archangle dancer, if of interest. There is a $2 + admission to St. Michaels. No whales in May and no salmon either- which attracts the the other wildlife. With your short time, you are probably better off hitting your listed attractions, making the most of your time. Consider purchasing the cheap Park Service guidebook re the pole at Sitka Heritage Park, will greatly enhance what the poles you are seeing are about. Request their visitor guide
www.sitka.org