Notching the bar will be fine.

And redrill that throttle cable hole, or pack out with small washers.
They are absolutely TERRIBLY made.

I realised the washers idea as I was dozing off haha
Should the spring rather be attached to say the cable side to purely be working on returning the linkage and cable rather than weber throttle

It's all connected inside anyway, so it won't really matter.
My spring is how you have yours (on the same side), but goes back to the firewall instead.