1. Yikes. Your wxWidgets DLL was compiled with debugging symbols/code.
2. Read the link I posted earlier.
3. If you take a look at the code of wxScrollingDialog you will see it does its magic by dynamically moving the widgets in the dialog into a scrolling window, BUT ONLY when you call "Show" or "ShowModal". By forcing your dialog to resize using Fit and SetSizeHints in your constructor, you are creating a warning because there is no scrolling window to dump everything into, but you aren't changing the size of the dialog because all of that will be undone when you call Show. You will also notice that wxScrollingDialog is hard coded to set the size of the dialog to the lower of the size required to show it or the display size. If you want to do something different you could try something like override Show/ShowModal:
bool YourDerivedDialog::Show(bool show)
{
if (CanDoLayoutAdaptation())
DoLayoutAdaptation();
wxSize s=GetSize();
SetSize(s.x,700);
return wxDialog::Show(show);
}
Anyway, this really isn't C::B development related.