1) yes, they would have to be to explain the interference 2) while altering the slits would definitely have some effect on the interference pattern, my interpretation would suggest that the parts which are “far away” are further away in the 4th dimension, in such a way that they wouldn’t have an interference effect and wouldn’t necessarily be “further away” in the 3D sense which would have anything to do with the distance between the slits 3) the test has been run with two individual detectors with the same result

Thanks for reading and for the questions!