Where do I install my hairpin legs on this 8 foot long butcher block for my new workstation desk?

So this is my first DYI wood project for my new workstation desk. I purchased this Baltic birch butcher block and finished it myself. Not bad for my first go! It’s 8 feet wide, 25" deep and 1.75 (1" 3/4) thick. It’s a heavy boy.

For my legs I purchased these 28 inch ones. They’re solid but the 1 inch dry wall screws that arrived with them are poor quality so I’m going to pick up some wood screws.

Questions:

1. Where should I install the legs from the edges? It says 2 inches from the edge. Will that be enough for an 8 foot wide heavy butcher block? I don’t see a problem with bowing in the center. Is there a rule of thumb for installing legs? I’m worried I’m gonna mess it up.

2. The holes in the leg plates are 1/4" in diameter. The desk is 1.75 (1" 3/4) thick. What kind wood screw size will do? Also, do you recommend I drill a pilot holes for birch wood?

Apologies for the super newb questions. Thanks a bunch!