Will my crowded teeth shift & spread apart after wisdom tooth removal?

Probably not. They will most likely not get better, but at least the crowding wont get worse. Hence it would still be worthwhile to get them removed.
Nope. Teeth want to move forward, not back. If you have crowded or crooked front teeth it would behoove you to see an orthodontic specialist to learn about all the ways teeth and jaws can be repositioned for health and appearance.
No. Because of the way the biting forces are aligned teeth will shift forward if a tooth is removed but they typically do not shift backwards.