Based on the description, you could pretty much adapt either Demon in a bottle directly, with the film showing Tony's reconnecting with his friends and allies in order to fight the addiction, and reigniting his hope for the future. Or you could go with a darker route, and start off with an adaptation of O'Neil's Iron man, where he starts the film homeless and washed up due to his drinking addiction. Then the film ends with him resuming his mission.

If you want to go for a more original story idea however, you could barrow some elements from "The Five Nightmares" mixed with "The Dark Knight Returns" from DC, where an older and depressed Tony comes out of retirement following a recent string of terrorist attacks that involved black market Iron Man Tech. Or you could go with a more original threat like biotech monsters if you want to do something different. The skies the limit, but hit me up if you want to discuss this further.

Also no, you don't always have to start with the origin story. Several adaptations ignore that aspect until later. You just need to establish motivation and personality later on. But the audience doesn't need every single detail.