Have you tried to reward him just for refocusing on you without prompt? Like if he checks in, do you reward him? That's something I've always done with puppies/new dogs. If they check in, huge praise and reward then give them the "all-done" cue and send them back out. I don't do anything to prompt it just be observant for when they choose to focus.
I'm thinking if you can increase your value as a handler it might help him pay a little closer attention and be more intuned to you all of the time.
Yep, I do that all the time. During any walk or any activity really (classes, going to a store) he gets heavily rewarded every time he focuses on me on his own. He's super impulsive, so the entire time I've had him I've tried really hard to reward him for making the right choice on his own, vs cueing it. It's worked really really well in obedience class to reward for a voluntary check in, work a little, then releasing him to sniff, and he's able to focus much more than he was before. Outside though, it only works if he's on a short leash. I will reel him in close to my side and keep him there until he makes eye contact, then he gets a treat or a release to go sniff. He's much better at focusing on me on walks now and doesn't spend the whole time at the end of the lead sniffing everything. On a long line and with recalls, nothing has changed. I think I need to use the same technique and reel him in on the long line, then keep him there until he makes eye contact and focuses. I honestly never thought to use the same thing on the long line.
On both long line and short leash, if he hits the end I will stop and wait for him to look back at me, or even come closer to me. Both are rewarded with treats, sniffing, or more walking. His rate of hitting the end of the long line doesn't seem to have changed with this technique. He'll gladly look back and refocus on me, and then charge out to the end to get whatever he wanted to get.
I completely agree that my value as a handler needs to be higher. Sometimes I think I must be a horrible trainer, but then other days I think he's just a really tough dog. He has more drive than I ever expected, and a lot of it is focused on hunting and prey, not on me. He's honestly super sweet and fairly biddable most of the time, but when he's tuned me out, he's really tuned me out. When he's engaged and focused, he's fantastic. When he's good, he's the most flashy dog in our obedience and agility classes. When he's bad, he's the worst dog there by far. lol