1. They can use more secured ways to identify the real identity of their customer, the best thing to do here, aside from valid ID is they should add "take a selfie" on identity process.
This is already implemented when verifying one's identity. The platform always ask to present a selfie or even a video interview to verify the person.
2. They can also set a time limit of playing for a player, give notification if this would be their last game anymore for today.
The problem with this approach is that a person can play in different platform so limiting them in one gambling platform have no effect because they will just move to another gambling platform to continue playing.
3. Set a notification showing how long they've been playing.
Some casinos have this notification. I have experienced this thing in some casinos when I was playing more than an hour, I received a pop up reminding me of how long I have been playing on their platform.
With these kind of features, they might actually help or lessen the addiction of a gambler.
I doubt it because a person hooked on gambling can easily bypass and ignore the 2 and 3 suggestions you made.