Re: Correct nut height measurements needed!
When I replaced mine, I kept the old to compare. If the old one fit right, then sand the bottom as described above until the string notches are the same. Don't try to sand until the top of the nuts are the same, the slot depths may be different. As for the gap, you have to make sure that where the fret board and nut meet, it is very clean. It also looks like you didnt sand the face. The back of the nut looks like its sitting too far back, which means the nut wont sit flat. You need to sand the face (that faces the fret board) until it sits flat. I'm also assuming you haven't glued it in yet if you haven't set the string height yet. The string tension you have on it know might be pulling in forward. Once you sand it and it fits well, glue it in before you put any strings back on.
2009 Gibson Historic R7 VOS Gold Top
2011 Gibson Joe Bonamassa Les Paul Studio Gold Top
2010 Epi Joe Bonamassa Les Paul Gold Top
2010 Epi Les Paul Standard '57 Gold Top
2010 Epi Les Paul Standard Honey Burst (autographed by Joe Bonamassa)
2006 Fender American Deluxe 60th Anniv. Jazz Bass
2005 Epi Dot
2004 Eric Clapton Signature Strat
2007 Line 6 Flextone III XL
1970's Peavey V-212 Classic
2010 Vox Lil' Night Train
2010 Fender Mustang II
1989 First wife (also a Gold Top)