I read a sutta (here it is Perceiving Nibbana, (AN 10.7)) saying the cessation of existence (bhava-nirodha) is Nirvana. If the cessation of existence is Nirvana, it cannot be impermanent and suffering.
Vibhava does not read as though it is the same as bhava-nirodha. Vibhava reads like it is a conceptual idea rather than an actual state of non-awareness. You wish to not exist; this is vibhava. Whether you really do not or will not exist you cannot know. If there is rebirth at the moment of death, how can there be non-existence? Your post sounds mixed up about Indian language.