Is it theoretically possible to wing from yamba to tweed. And if so, how long would it take in the winds that are needed to do this?

This is a serious question, no idea how wing foils work.

Yeah it would be doable, all in one day would be pushing it. 180km from Yamba to tweed so doing 25km per hour you would look at roughly 7hours. You would want a good solid day of wind from early morning and it would be doable. Maybe more fun to break it over 2 days.

I did north solitary island to run away bay in a 40 ft cat in 24 hrs. What ever floats your boat.

James Casey has done just south of Wollongong to Palm beach, at roughly 100km, just a couple of hours at decent pace. I wouldn't be surprised if we start to see Mereweather back to Long Reef in a decent NE'r.
Either way - if you want to do it, do it!