UV/Image Editor grid snapping What is the way of emulating the Snap to Grid feature from the 3D Viewport in the UV Image Editor? In my case, vertices of my mesh are never aligned with gridlines, which in turn results in some artifacts on whole scene. 

Also there is not consistency in mesh shape if perform "Lightmap Pack" as can be seen from image. Some of the actual mesh faces are more kite shaped, but map as squares or rectangles when it's "Lightmap Pack" unwrapped.
You can use the texture image as a grid. In case you have no image loaded, create one. Then activate Snap to Pixel in the UV's menu. And when you move the UV vertices around in the UV Editor, then they will snap to the pixels of the image now.

For the other questions i would suggest to open other topics.