Addicted gamblers are often very secretive, if they are open they may have to take responsibility and that is so difficult. They don’t want to be addicted, they would love to gamble responsibly like so many others do but it is not and never will be possible for them.
However, your ex is also secretive about, what appears to be multiple, affairs he has had in the past and this is setting alarm bells ringing for me.
In my opinion, trust is important in a relationship and I don’t hear trust for your ex in any of your posts and I also don’t hear any reason for him to deserve your trust.
I suggest you ask yourself why ‘you’ feel guilty about leaving him alone?, by detaching and allowing him to face his demons and determine what he wants to do with his life is, in my opinion, the best thing for both of you. If he abuses his freedom then it is down to him, not you.
Ask yourself why “I am stuck in a very desperate and unhealthy spiral of wanting to move on and wanting him back” when you are exhausted from ‘his’ indecision.
What do ‘you’ want Melanie? I am not asking what your ex wants or anybody else, just you.
I suggest that you are tired of the pain this relationship has brought you, not just the gambling but another woman and so many lies. Maybe you still feel you can save him but sadly you cannot save him and that is a fact. The only person you can save Melanie is ‘you’ and believe me you are worth it.
Keep posting, you are doing well