1 year is not too old.
Loose leash walking is a walk in progress. I would advise you to google or search youtube for "Loose leash walking" training tips.
Treats are good as an incentive, but its the owner's reaction, methodology which matters most.
Frequent stopping, turning, when ever you feel the least bit of tension on the leash. Getting the dog's attention when you are walking with him, etc are important points.
Also, when you are training your dog (and yourself) to walk on a loose leash, please make sure you are going for a walk with your dog, not for grocery shopping, not for anything else.
Also, your dog is naturally protective. When he sees another dog, there is bound to be a response. You can counteract, by showing him you are the leader of his pack. Stay calm, collected. Your dog cant understand your human language, but he sure can read your body language. Trust me, body language is the most key thing here.
When my wife sees a dog coming from the distance, she is hesitant and thinks about moving to the other side of the road. Naturally my pup reacts badly. Whereas, I am calm, keep talking to who ever is walking with me, ignore the other dog. But I do give the leash a tug or two to make sure the pup knows I am here and in charge.
My pup never lunges at the other dog.
Its a work in progress, loose leash walking and a calm demeanor is attained from a long period of learning for both owner and dog. I am sure you will succeed.
Please keep in mind there are no "magic shortcuts". Prong collars are great, but not the magic solution. Its you ... and how you train your dog.