If the target creature is an illegal target as Bile Blight tries to resolve, it won't resolve and none of its effects will happen. No creature will get -3/-3.

Bile Blight has only one target. Other creatures with that name are not targeted. For example, a creature with hexproof will still get -3/-3 if it has the same name as the target creature.

Unless a token is a copy of another permanent or was explicitly given a name by the effect that created it, its name is the subtypes it was given when it was created plus the word "Token." For example, if an effect creates a 1/1 Soldier creature token, that token is named "Soldier Token."