Hi MazaaFIN, first of all well done.
If you modify a thing which was open source (right now I don't know if the license was CC-SA or MIT license or whatever), you have to release it opensource again.
Even tough I can't understand why you don't want to share the SolidWorks file, could you at least post plueprints or even step or IGES files? I could tell you what modifications to implement but then it would be complicated because I will print and test and then give feedback...
It's boring to do the reverse-engineering on the STLs I hope you could provide at least the plueprints