Patur Aval Assur–
1) as you well know that is a straw man right there. You were saying that within the Maharal you can read that it means Gezeirah not a halacha. I brought you proof that when the maharal uses the word Gezeirah like he does in this context it for sure does NOT mean that it is not halacha. He saying the Hashem was Gozer this issur and if we do not keep it, r’l, what could happen.
2) Not sure I quite understand the Rav Shlomo Kluger. Why was shevet Ephraim punished then? Anyway this is only talking about the Shevua of Dechikas haketz which was the only one in Mitzraim. But by us, (i.e our galus), we have an additional shevua of shelo yaaleh K’choma.
3) I have seen what R’ Kasher wrote. To be respectful lets leave it at that they are shver.