I do not know why the slope you calculated with your heavy spike in calibration curve would not produce meaningful numbers with your light data.
You should send us your Skyline documents and we will figure out what is going.
In Skyline, you can use the menu item:
File > Share > (complete)
to create a .zip file containing your Skyline document and supporting files including extracted chromatograms.
If those .zip files are less than 50MB then you can attach them to this support request.
Otherwise, you can upload them here:
Skyline-Daily added some new features related to calculating LOD and LOQ. To use this feature go to:
Settings > Peptide Settings > Quantification
at the bottom of the Quantification tab on that dialog, there is a "Figures of Merit" section where you can specify the maximum CV etc.