Your spare hole? I presume you want to plug it in to an amp? The rear one is where the jack socket goes.
I wouldn't worry about any minor gaps like the one in your picture below. It's very likely the gap will disappear when you clamp and glue it. If not, it's small enough for finish to cover and fill the gap:
1= pickup ring mounting screws
2 = strap buttons
3 = truss rod cover, solder and various screws and washers for the pots, jack and switch.
4 = mounting screws and washers for the tuners
5 = Bridge posts and bushings
6 = volume pots (a500) tone pots (B500) and output jack
7 = pickup selector switch
8 = stop tailpiece posts and bushings