If you replace your add_colorbar function calls by this:
plt.colorbar(kde.collections[0], shrink=0.8, orientation='horizontal', location='bottom', pad=0.05, anchor=(0.0, 0.5))
plt.colorbar(scatter, shrink=1.0, orientation='vertical', location='right', pad=0.05, anchor=(0.0, 0.5))
You will get: