I think you read the multimeter wrong because I almost guarantee you have a dead battery. The ABS and airbag light, along with the battery light indicate a charging problem meaning your alternator likely went out and then killed your battery. Also a battery is not going to have 15 volts sitting static.
Something else that may be happening is your terminals could be corroded. I have ran into issue where the car all of a sudden acted like the battery died and wouldn't even start jumping it. Once I pulled the terminals off and cleaned all the contact points up it fired up without issue.