- Leniencies aside, are there levels of non-kosher food?
For example:
- In case of need, is it better to eat chicken road kill than rabbit road kill?
- In case of need, is it better to eat cheeseburger than bread on Pesach?
Yes, there are multiple levels.
In the Laws of Forbidden Foods 14:16-17, the Rambam writes:
"When a person is overcome by severe hunger, he may be fed forbidden food immediately until his eyesight clears. We do not seek permitted food. Instead, we hurry to feed him what is available.
"We feed him substances bound by more lenient prohibitions first. If his sight clears, that is sufficient. If not, we feed him the substances bound by the more severe prohibitions.
"What is implied? If there is tevel and a nevelah, we feed him the nevelah first. [The rationale is] that [partaking of] tevel is punishable by death [at the hand of heaven]. If [the choice is between] a nevelah and produce that grows on its own during the Sabbatical year, we feed him the produce, for it is forbidden [only] by Rabbinic decree, as will be explained in Hilchot Shemitah.
"If [the choice is between] tevel and produce grown during the Sabbatical year, we feed him the produce grown during the Sabbatical year. If [the choice is between] tevel and terumah, if it is impossible to make the tevel acceptable, we feed him the tevel. [The rationale is] that it is not sanctified as terumah is. Similar laws apply in all analogous situations."