Firstly, the accuracy of the location of a point depends on the signal of the GPS device. Generally speaking, if there is a 3G signal, the signal of the GPS device is good. Of course, you can control the accuracy from the settings, but if the signal is not good, the accuracy would be as good as the signal is!
Every time you want to add a point press the "+" button.
In the current version, iPinPoint can measure the magnitude of an angle, and the distance between two points or the length of an object. You need to add 3 points to measure an angle, and two points to measure a distance. In the case of an angle, the second point is the angle vertex.