There appears to several parts of this interpretation that appear confusing for you;
1/ The Islamic Dispensation from the Hegira (622 CE) to 1260 AH (1844 CE)
The first day of the first month of the Islamic calendar (1 Muharram 1 AH) was set to the first new moon after the day the Prophet moved from Quba' to Medina (originally 26 Rabi' I on the pre-Islamic calendar) i.e., Friday, 16 July 622 AD/CE, the equivalent civil tabular date (same daylight period) in the Julian calendar. The Islamic day began at the preceding sunset on the evening of 15 July.
Islamic calendar - Wikipedia
2/ The conversion of days to years in biblical prophecy
3/ The reference to 666 in reference to an empire that began in 661 CE
4/ The actual birth date of Christ was 4 - 6 BC rather than at the beginning of the Gregorian calendar.
5/ The use of the actual birth of Christ than the start of the Gregorian calendar to determine a 666 year interval. ie from the birth of Christ to the start of the Umayyad Dynasty is 666 years.
6/ The Umayyad Dynasty lasted only 749/750 CE and not for the entire Islamic dispensation.
7/ The use of cryptic symbolic language through out Revelation.
So the Umayyad Dynasty killed the spirit of the Islamic Dispensation as well as murdered Ali and other Imams who were the rightful leaders of Islam. So they killed Muhammad's Teachings figuratively and Ali/Imams literally and figuratively.
The 3 1/2 days is a Messianic reference liking Muhammad's revelation to that of Christ. It's use is very clever because it also represents 3 1/2 years so 42 months/1260 days. So The sacrifice of Christ is linked to the Divine nature of Muhammad's Revelation and the sacrifice of the Imams.
Remember the Hegira was to flee from the Quraysh and the Islamic dispensation is characterised by corruption as symbolised by the beast.
Sodom and Egypt are also Messianic references, so once again linking the Revelations of Christ and Islam, the martyrdom of Christ and the spiritual death of Islam.
Abdu'l-Baha explains;
“And their dead bodies shall lie in the street of the great city, which spiritually is called Sodom and Egypt, where 11 “Their bodies” means the Religion of God, and “the street” means in public view. The meaning of “Sodom and Egypt,” the place “where also our Lord was crucified,” is this region of Syria, and especially Jerusalem, where the Umayyads then had their dominions; and it was here that the Religion of God and the divine teachings first disappeared, and a body without spirit remained. “Their bodies” represents the Religion of God, which remained like a dead body without spirit.
Bahá'í Reference Library - Some Answered Questions, Pages 45-61
