From what you've said it's going to be tricky for anyone to say exactly what springs you have.
As for fork oil, answers range between 10w and 15w oil, and someone will almost certainly point you to this viscosity table to point out that not all bottles with 10w written on them contain fluid that's the same:
http://www.peterverdone.com/wiki/ind...spension_Fluid
For me personally with stock forks and slightly stiffer springs I found 10w to be a little soft, 15w to be a little harsh so mixed a bottle of each together and filled my forks with that, which I quite liked. Others would prefer their damping a little firmer, or softer and no one would be wrong.
Personally, I'd stick with the stock air gap (which is somewhere around 110mm from memory, but this will possibly depend on if you have an SV650 or SV650S) unless you have a reason to change it. You will need a little less than 500ml per fork.
Jambo