Somebody is certainly bringing alot of extra baggage and drama and chaos into a new relationship. That for me would be a red flag in itself.
If he is done with the ex, he needs to move forward.
Don't understand why you need to be kept a secret, that tells me something is unresolved. Please proceed with caution.
When someone threatens suicide, take the threat seriously, and report it to the police, allow them to deal with the situation.
We truly cannot control the actions of another, more importantly, we do not have to live in fear and guilt of another's choice. This is how this horrible disease controls lives.