Which wasteland creatures would and would not be treyf?
The vast majority of Wasteland creatures are NOT suitable for eating under Torah law, let alone rabbinic law, for fairly straightforward reasons - land animals must have cloven hooves and chew cud, which basically counts out all reptile-derived creatures (e.g. Deathclaws, Geckos), human-derived creatures (e.g. Centaurs, Tunnelers), and obligate carnivores (e.g. Wanamingos).
Brahmin, Brahmiluff, Bighorners, and Radstags should be kosher; despite their mutations, they are still recognizable as ruminants, and to my knowledge maintain an herbivorous diet.
For seafood to be kosher, the animal must have both scales and fins. Surprisingly, this means you could argue that Lakelurks are permissible as food - though I doubt most rabbis would actually take that stance, given that no kosher fish has arms and legs. It doesn't look like Anglers have fins, and Mirelurks have neither, so they're unquestionably treyf.
Insects are generally treyf, though certain species of katydid, grasshopper, cricket and locust are acceptable. Therefore, Cazadores, Bloatflies, Bloodbugs, etc. are not kosher. Cave Crickets might be okay, though!
Scorchbeasts are derived from bats, which are treyf, so they would almost certainly be treyf by extension.
Most cryptids, being land creatures that lack hooves, are treyf. The Sheepsquatch, while bipedal, has cloven hooves and presumably still chews its cud, so I would say it's kosher. You could argue that the Mothman is either "basically a big moth" or "basically a weird dude," but both of those would be treyf anyway, so it's academic.
Vegetables, fruit, and fungus are generally kosher by definition - though my understanding is that certain fruits, such as blackberries, are not recommended by kosher authorities because it's impractical to check if insects have gotten into them. Because of this, you could eat spore plant pods.
However, spore carrier sap, being secreted from a highly infectious creature that consists partly of a human corpse, is basically the most treyf thing I can imagine. You're not only running into issues of dietary law, but also handling of corpses, self-preservation, and possibly leprosy.
Crows and seagulls (and therefore radgulls) are treyf. Chickens are kosher.