Hi Romana,
I believe Velvet can give you better advice than me, from her replies I can see she is the specialist in the family and friends part.
based on what you wrote I really have concerns, because I think he still in the pre-contemplation, he still thinks of gambling as a solution for his problem, he still trying to have access to money to feed his addiction, and regarding the money that he borrowed from you, I believe he will return it once he gets his life together again, he is not a bad person he is a good person with a bad problem.
in his mind, he thinks that he will take this money he will gamble it and “win” and then he will return the money back and solve part of his financial issues with what he won, this irrational thinking will lead to losing more and more,
the point at which the change will start is when he will admit that he has a problem, and gambling is not the solution to his problem, in fact, it is the problem itself. and he has to stop gambling completely at this stage the recovery starts and you can work together to fight this addiction. which is not an easy way, it is a long and hard way.
Romana, I am really touched by your story because you still at the shores, you are not a gambling addict, you are not yet the spouse, and the gambler is not a brother or father or any other family member. you can just walk away and avoid the suffering that this addiction may bring to your life.
but you chose to give him a chance, and you are searching and trying to understand how to deal with this addiction. I think by now you have a better idea about this addiction and you can take your decision. and remember don’t be emotional your life is the priority and then the others.