1| Since we're dealing with the LGA2011 platform the only chipset and effectively the motherboards available for you are those based on X79 chipsets.
2| The best source would be to look through Ebay or other second hand exchange/classified sites since buying brand new
older gen hardware often means that they are rare and subsequently overpriced for it's feature set but be careful when buying second goods, since they often come with broken or bent CPU socket pins.
3|
Here is a list of boards your processor will fit into.
4| Can you pass on the rest of your components in your build?