Just to get the less complex stuff out the way, I will respond to the point about shiurim first, and then move on to the reshus harabbim issue in a future post. On pages 262-264 of ‘The Laws of an Eruv’, the authors note that the minhag in Europe was to use a shiur ammah that was near the Chazon Ish shiur for eruvin. They also bring show that Reb Yaakov Kamenetsky and R. Moshe Feinstein used shiurim that were larger than R. Chaim Noeh’s but smaller than the Chazon Ish’s, and that these shiurim are used in many communities outside of Israel bein lekula bein lechumra.
Rav Elyashiv himself recognised the legitimacy of this tradition when he issued a clarificatory letter regarding the NW London eruv. Rabbi Eider planned the NW London eruv using the same measurements he always used, but unfortunately certain inshei deloi maalei (who were later shown to be such) saw this as a convenient issue to latch onto for their own nefarious purposes, and had no qualms with distorting the historical record when doing so.
There are many misconceptions that people have regarding the larger measurements for a shiur ammah in general – for a start they were generally not taken on as a chumra, and they don’t even necessarily require using a larger shiur for kezeisim (as a thorough examination of the Chazon Ish’s position demonstrates). I’m happy to supply marei mekomos to anyone interested.