We rescued a Malinois who has amazing food drive indoors but none outdoors. How can I build more confidence in him?

I would work him in a distraction free environment while you build a relationship and communication system. I like to teach all my puppies and dogs to engage with me on cue, this is especially comforting for dogs that are nervous or have confidence issues. It gives them comfort because if you do enough of this to build an automatic response, they feel good because they know what comes next. (if that makes sense)

I'd suggest watching The Power of Training Dogs with Food, it's the foundation for everything I do with my dogs. Don't get in a hurry to take him out into new environments, work on getting and keeping engagement in a no distraction setting for a good long while. Remember that movement is motivating but resist the temptation to 'test' him outside for now.

I adopted a 9 year old dog that had no training and successfully created a dog that loved to work thru the use of food and the techniques shown. For now you just should focus on effort, engagement and relationship building and later this will make training obedience behaviors easy as long as you are using the right motivator for the dog and keeping sessions short at first. I'd rather do 10 two minute long sessions a day than a few long sessions. I hope this helps.