I guess the only way you'll really know is when he starts ruining your encounters with it. When that happens, you'll know you goofed.
Do the ingredients of this poison come from some natural source, or is it Magical? Is he BUYING the components? I mean, at 1000gp per dose, you've set it higher than Purple Worm Poison. How many Purple Worm hunters out there? Should be VERY dangerous to get the components (from a source with better than a CR12). If this is a Magical Poison, there's a Feat for that. Follow standard Spell Creation rules.
Honestly, the 2d6 rounds duration is only important if your guy just wants to "circumvent" the opposition. If he's going to CDG them anyway, it could be only 1d4 rds and probably wouldn't make a diff.
If I was going to make this poison from the ground up, I'd start by looking at an existing poison, and modifying it. For example: Carrion Crawler brain juice is a "contact" poison that paralyses. DC13, 200gp.
Making it 3 rds duration (equiv to 3 "doses"), triple price = 600.
Requiring only 1 hit (instead of 3), same again, 600 + 600 =1200.
Injury type poisons
tend to be less expensive than Contact types, so you could reduce the cost. However, this would be for a DC13 poison. Raising DC would increase the cost again.
In any case, Good Luck.
