I'd like to join Maddeline in welcoming you here. It is a heart-breaking situation and one where it can be very hard to gain perspective as you love the person he was.
You mentioned having kids, and ideally for that you need a partner you can trust and rely upon, one who helps, is never a threat, and is a support when one feels overtired and overcome by it all.
Sadly you have a partner who is addicted to drugs and has a very adverse and extreme reaction to them. It is an addiction and as such his promises do not have real meaning. you found this out when after the second time he took the first opportunity to use again
You talk of putting yourself first, and naturally feeling guilt as a result. There are a couple of points you might like to consider.
The first is it is not just looking after your own welfare, but that of any children you may have - who too will need a stable, safe and loving life.
The second is your account implies he is becoming more aggressive and controlling, and I'm not in the least surprised it raised a flight or fight response. It can be very frightening when the one who should be closest to you becomes a danger. I'd be frightened too.
I'm glad in practical terms you could involve his mother, and he ended up with treatment, unfortunately its effects did not appear to last much beyond the compulsory period.
I hate to be blunt however it is only fair to you, and that is to say if you were to leave (and even under these circumstances that might be no easy thing) then there will be periods of guilt. You may know logically it might be the solution, but emotion does not always follow logic.
Is there anyone you can talk this over with? A friend, family member or even your GP? It can help.
It can also help to get someone experienced with the drug use involved to say what the likely outcome could be. Maybe your GP, the doctors in the psych ward or a state run drugs and alcohol bureau might be prepared to give advice in general terms.
If in doubt please ring our own 24/7 help line on 1300 22 4636 who may be able to steer you towards suitable resources in your own area