[@Sigil]
So I thought I had the math right. Below in the hider is my attempt at explaining my stats.
[hider=My math]
1) All stats start at 13
STR 13 DEX 13 CON 13 INT 13 WIS 13 CHA 13

2) Raise DEX four points to 17, at a 1:1, dropping STR by four 9
STR 9 DEX 17 CON 13 INT 13 WIS 13 CHA 13

3) Raise INT by two to 15, at a 1:1, dropping CHA by two to 11
STR 9 DEX 17 CON 13 INT 15 WIS 13 CHA 11

4) Raise INT by one to 16, at a 2:1, dropping CHA by two to 9
STR 9 DEX 17 CON 13 INT 16 WIS 13 CHA 9

5) Raise CON by one to 14, at a 1:1, dropping STR by one to 8
STR 8 DEX 17 CON 14 INT 16 WIS 13 CHA 9

6) Raise WIS by one to 14, at a 1:1, dropping CHA by one to 8
STR 8 DEX 17 CON 14 INT 16 WIS 14 CHA 8

7) Apply Racial Bonuses, +2 to INT for being a Gnome, +1 to DEX for being a Forest Gnome
STR 8 DEX 18 CON 14 INT 18 WIS 14 CHA 8
[/hider]
So if my math is off let me know. I think the issue was you didn’t note that Gnomes get a bonus to INT.

As for the weapons, I don’t know. I’ve never played a small character before. I just assumed that like his armour, it was appropriately sized for a Gnome. I am not sure if that would affect its stats, I think that would be something you as the Dungeon Master would have to make a ruling on.

Hopefully that sorts out my character. Please let me know if anything else needs editing/explaining.