Answering in simple Jain terms:

1. Which is more – Bhavya or Abhavya jīv?

Jain philosophy says that most souls are Bhavya (भव्य) – capable of attaining moksha sometime in the infinite future. Abhavya (अभाव्य) souls – who will never attain moksha – are said to be very rare. So, in number and in spiritual value, Bhavya jīv are “more”: - more common - and more “fortunate,” because they can one day become Siddha.

1. Can a Bhavī jīv become Abhavī?

Here we must be precise with words:

- Bhavya / Abhavya = type of soul (capable or not capable of moksha). - Bhavī / Abhavī is often used loosely in pravachan for “one who will get moksha / one who will not,” but in tattva, the main division is Bhavya vs. Abhavya.

According to Jain doctrine: - If a soul is Bhavya, that means it has innate capacity for moksha. - That capacity does not get cancelled later. - So a truly Bhavya jīv does not become Abhavya.

What can change is: - A Bhavya jīv may wander in saṃsār for an extremely long time, behaving like a non‑spiritual person, so it looks “abhavi-type,” - but the inner potential (bhavyatva) remains. One day, when strong deluding karmas weaken, samyak darshan can arise and the path to moksha starts.

Only a Kevalī really knows who is Bhavya or Abhavya; we should always consider ourselves Bhavya, and make effort in: - ahimsā, - samyak darshan–jñān–chāritra, - reducing anger, pride, deceit, and greed.

For a simple explanation of Bhavya and Abhavya jīv, you can read more here