Gearing to position in dropouts

Ok kids,
I want to do this in theory before it becomes an ordeal like everything I do on my bikes does.
Searched but to no avail, I got a new(to me, three months old) Fuji track and as you may or may not know it comes with the ol' 48-16t gearing.
A bit too high for me on roads so I decided to go a bit spinny on this compared to my conversion.
I got a 18t sprocket today and was wondering how much(roughly or not) does the wheel need to move per tooth.
The wheel at good tension is sitting about half way in the dropouts and I recon I will need to add a link, so another question, how much movement in the dropout does the link (+ or-) make?
Cheers,
Stein.

Might help: http://www.londonfgss.com/thread11284.html

1 tooth = 1 extra pin in chain lenght = 1/2" or 1/4" forward in dropout.
2 extra teeth (16->18) = 1" or 1/2" forward in dropout.
If you don't have that room to move add a link, but I would use an extra connecting link (the type with clip retainer) rather than try and join a new link with a push-fit pin. Or buy a new chain and keep this one for when your legs are bigger :)
48/18 is a good all-round gear for town but not so good for skidding as you only get 3 skid patches... 46/17 is close in overall gearing, no skid patches (you can't divide into the ratio) and you wouldn't need to lengthen the chain... but you would need to go shopping.
^ of course there would actually be 17 skid patches but that's enough for them to be spread over most of the tyre!

Wait... I have the 08 model and in that thread(thanks hippy) people say its 15 tooth...

I've got a Fuji that came with 48x16. It's not running 48X18 and works perfect. Done. End. Do it!

Oh also another quick question, I got the bike and noticed that the chainline was out immediately.
Now the chainring needs to go out further but it is already on the outside of the spider.
Brought the bike to a bike shop today and they pointed out that my bb is askew(to the non drive side) and told me I had to take off the bottom bracket and put in a spacer(which they gave me) on the drive side.
This seems like allot of effort since I have none of the tools to do so.
I have thought of re-spacing the wheel but that would mean I need to re-dish it, something im also not up for doing.