We seem to be coming from widely different places. The matter content has been measured. The standard LambdaCDM model gives the simplest good fit to the data and Lambda has been measured. From my perspective the distance to the cosmic event horizon is known---as I recall some 15 billion ly.
Your attitude seems to be that we cannot answer the original question because we are free to play around with the matter content and get a different distance to the CEH.
Well...that's how you think about it. Lineweaver, the author I cited, simply answers the question based on standard cosmology. He's a working cosmologist, using the best model so far. He uses the 15 billion ly figure, or thereabouts, as I recall. The answer is provisional, like everything in science---the model subject to improvement of course. But I doubt the rough order of magnitude estimate he gives is going to change much.