With curve fitting you try to apply a model to your measured data. Since interaction kinetics is described by a 1:1 langmuir reaction, this is the model to use. When your data is following 1:1 kinetics the fit will match your curves. The fit will also give you some parameters which describe the curve in terms of association and dissociation rate constants. These two you can use to compare different interaction conditions or proteins.
I suggest you start with reading
www.sprpages.nl/data-fitting.html
. With the T100 you will use probably the non-linear regression.
Your second question will be answered on
www.sprpages.nl/data-fitting/validation.html
(I hope).
I can suggest to buy the SPRpages book with more information on this topic.
kind regards