Hi I was just wondering if someone could answer this quick question

Can I make my merchant never move from the spot I've placed him?

kinda ... have a look at any AI packages your merchant has (AI Packages Tab). Check through each one to see whether it allows moves.

AFAIK: Merchants don't need packages, so you could remove any present and the guy should stay in place.

You might want to add an idle package, so that he has a few moves, on the spot, that he can make.

You could rip out all his AI packages and he will stick to the same spot. Much better to have a little routine or give him a short range sandbox package though imo

http://www.creationkit.com/Bethesda_Tutorial_Packages

You could create or duplicate a package that tells your merchant to hang around a marker or an item (chair, forge etc)

I've got mine sleeping, eating twice a day, picking flowers, sweeping her porch and sitting on the dock.

Oh apparently in the range box 1 = 1 cm is that correct?

What's needed for creation a merchants.
1.Create container
2.Create faction
3.Create NPC