Need Help with Our 1 Year Old Brittany Spaniel

Hello. We have a one year old Brittany Spaniel named Riley that we got from a respected breeder when he was three months old. There are things we love about him: good with kids, consistent recall, doesn't bark, and is super sweet. Our family has an active lifestyle and a quarter acre fenced in yard. The thing that is so hard to handle is the prey drive and on leash training. We've tried pinch collars, no pull harness, and a halti collar, but nothing seems to work at all. Walks have become miserable as he pulls non-stop. He also seems to focus much more on the horizon and looking for prey than our family. I've heard that they mature later and that part of this is his teenage years, but we're honestly starting to lose some patience and feel he's making our family life significantly harder. I've had several dogs before and felt more connected to them than Riley. I'm not ready to give up yet and look to rehome him. Any advice on how to handle a high energy Brittany? How much do they mature at age 2 or 3? Thank you.