I suspect Jo has turned from OCG to deep UCO.
When she asked for Kate's gun, she already had Ryan's gun (she gives it up after the car chase), so she's not asking for it because she wants to prove to Kate that she won't shoot her. She could have shot Kate already with the gun she took from Ryan.
I think Jo's mum went "missing" to encourage her to join the OCG in the first place. Suicide doesn't make sense.
I suspect Jo found out her mum is in Spain with Thurwell (who she had assumed was her father). And her mum was in on the plan to convert Jo to OCG.
So she's turned UCO to bring in the entire ring.
Now she's exposed as OCG she can't continue to investigate (I.e. get the evidence to bring in the OCG) So she's told Kate abs taken the fall for Ryan so the Kate can take over evidence gathering.
I think Carmichael is her handler. She was disrupting the interview to stop Jo caving and revealing information. So Jo won't (yet) be killed in prison by the OCG, as she hasn't revealed details of any living OCG members.
Hence Carmichael's "I'm pragmatic" comment to Kate. To let Kate know that she's aware of the truth and what Kate's aiming to do.
I also suspect some kind of redemption for Buckells. He's been in the background all the time. I wonder if he's been part of deep UCO for AC for a long time. Pretending to be totally dim so the OCG don't see him as a threat.