Regarding point 1, with m43 having half the diagonal length of FF you get the same FOV at the same distance when using half the focal length. So a 90mm macro on FF at its minimum focus distance will give you the same image as the 45mm macro at that same distance. When you only care about FOV then there really is no major difference except for FF having more and larger pixels. Of course with the m43 lens you have the option to go even closer until it reaches its 1:1 imaging point where the frame is filled by an object halve the size of what you can capture with the FF macro lens. Some consider this as a gain of apparent magnification others as a loss of effective FOV (capturing a smaller piece of what's out there). In the end people are taking great macro images with both types of camera and I decided that finding subjects and selecting the shooting/lighting conditions is what matters more than sensor size.