So much pee

We have an Aussidoodle that we got from a family friend, he turned one in November. He has never been fully housetrained and it is killing us. He does perfect with pooping, but the pee oh my gosh so much pee. He pees a trail through our house at least once a day. He's not leg lifting, he's not marking, he's not squatting and fully emptying his bladder. He just dribbles a trail then runs and hides. Once we get him outside he squats and finishes peeing.I have read the wiki so I know it's not guilt it's a reaction to us when he hides. He is doing this if it's been 2 hours or 2 minutes since we took him out. There is no rhyme or reason. He also pees in his crate no matter how long he's in there if we leave, but sleeps all night 8+ hours just fine with no accidents. We recently talked to his groomer because she is very experienced with poodles and doodles. She said it's very common for them to have anxiety and he may be anxious due to be scolding for accidents when we were attempting to potty train. She said we get upset when we see the trail of pee so he gets submissive and pees more. She suggested a belly band during the day so if he does have some dribbles we won't see it immediately and react so he eventually learns not to be on edge all the time and hold it better. We are trying that but he now starts to pee the second we take it off instead of waiting to go outside. She also said some dogs are almost 2 before they can fully control their bladder? But I thought it was 16 weeks when they could control it? I just know we are at our wits end and honestly thinking or re-homing him because we can't live like this. Any help is appreciated!