If we pretend that the "fish of the zodiac" per the 1915 translation is Piscis Austrinus (ignoring that it isn't a zodiac sign, and go along with his wrong calendation, and ignore the solstice), it still isn't good for his alternative chronology for 512/511 BCE.
Obverse
Line 2 (4 Apr 512 BCE), Saturn is actually between Aquarius and Capricorn, quite far above the southern fish, and also behind it, as made more obvious once the fish sets below the horizon before Saturn.
Line 9 (4 May 512 BCE), Saturn is still far above and still behind the southern fish.
Reverse
Line 5 (24 Jan 511 BCE), Moon is in Pisces, not the southern fish
Line 17 (7 March 511 BCE), no planets in the southern fish, Mercury in front of Pisces (after sunrise) but too far from the band to be considered entering.
Line 19 (14 March 511 BCE), no planets in the southern fish. Mercury within the band of Pisces (not observable, achronycal and in line with the sun). Position of Venus also not within the band of Pisces.
Of course, he'll probably say the dates are wrong (probably won't provide the dates he 'really' means either), and will probably say the 'fish of the zodiac' is sometimes Pisces and sometimes Piscis Austrinus and you 'just have to know'. Or some trash like that. But maybe he'll surprise me.