The best explanation I've heard is that it was a sterile hybrid of two Ferula species. Many Ferula have a long history of mythology behind them. Asafoetida (aka hing) is probably where the heart symbol came from (its roughly heart-shaped root was used as an aphrodisiac).

Silphium similarly had much demand as an aphrodisiac.

This hybrid likely grew in the African Mediterranean and the high demand for it, alongside its inability to reproduce through seed, is probably what led to its extinction.

Could be but the central bulb as made on the coins is unlike a fennel https://en.wikipedia.org/wiki/Silphium , and since this imaginary recipe is a part of a comedy it is unlikely to be edible. If you look at other ingredients they can surely make someone sick.