5-month-old Mini Goldendoodle – Walk/Run help

I am struggling to get my 5-month-old Mini Goldendoodle to walk properly. Here is a breakdown of his behavior:

• Walking away from the house: This is always a struggle. I usually have to cheer him on, lure him, or gently pull him to keep him moving.
• Walking toward the house: He bolts and pulls me the entire way back.
• On our street: He is generally fine as long as the house remains in sight.
• Running: He loves running instead of walking. He bites his leash while running and runs in a zig-zag pattern, which makes me afraid I’ll trip.

I tried taking him to a park to remove the "house" variable, but he just replaced the house with the car. He refuses to walk away from the car and pulls me back toward the parked location.

Motivation & Training:

• Food: He has low food drive; he only likes a few specific treats.
• Toys: He loves balls. I’ve tried tossing a ball ahead of us to encourage him to move forward. He will find the ball, but he won't fetch it—he just sits next to it. So, then, I walk up to him, throw the ball further ahead and he will go find the ball and so on…

What should I try next to help him feel more confident walking along with him?