The spell would confer exactly what it says.
Your base attack bonus becomes equal to your character level
As a 30th level Fighter, your BAB would become +30. You would still only have 4 attacks a round however, but considering AC of epic-level monsters, that is a decent buff.
Note: None of the three options you have given are applicable. The rules for Epic Attack Bonus have no sway over the spell granting you a BAB of +30 (since you are level 30). Your BAB from class levels and your EAB from class levels are simply different from the spell. I would say Option 2 is correct, but your "why's" for option 2 are confusing me.