My main comment was going to be that you hadn't mentioned him being neutered as I thought that could calm him down a lot. But you have done that, so my next question is was he from a working Labrador family, or a many seasons pet lab? Because working labs need lots of stimulation and exercise. I know it sounds like you are devoting a lot of time to him, but it has changed quite a bit with the different trainers (I'm not blaming you at all for this, the ideal would be that every breed has a well established and confirmed standard that all trainers train to, unfortunately I have never heard of this happening across the board, but If anyone has I would love to know about it please).
I wish (as a family - live in - member to a now old man lab) that I had some advice I could give you. Ours did stop mouthing his usual family members within the first year, but when someone came to visit that he hadn't seen since he was a younger puppy, he would get all excited and nip their ears and noses like he used to. That would elicit a loud yelp from the human and immediate hands down, and ignoring Ddog until he calmed down. The initial yelp seemed to stop him in his tracks, so that seemed to work well.
If he comes from generations of pet labradors, I think I would try and stop having professional trainers for a while, maybe he might benefit from things being a bit more relaxed for a while, which might help you to feel more relaxed too. I am not suggesting giving up all training, but maybe stick to the basics both while at home and outside for a little while. Ours never managed a reliable recall - if food was being offered elsewhere his selective deafness was amazing! So unfortunately he only got 'off the lead' time in his own garden (obviously), and in out of the way, and not near to roads, countryside. I have heard that in the US they have enclosed grassy areas just for dogs (and their humans!), I wish we had that in England. As our Dboy is not off the lead in public, we didn't have a problem with him jumping up at strangers, and at home all his human family loved the way he greeted them! With the younger children we held him by the collar until he had a chance to greet them gently, and after that he seemed to understand not to be 'jumpy' with them. I am using past tense because our poor dear thing is too arthritic now to jump at people, but he still has a great tail wag 😊
As for his feeding, from the very start we would move his feeding bowl away from him, part way through, for a few seconds, and sometimes stroke him while he was eating, as we never wanted him to 'guard' his food. He has never once shown aggression with his food - except for when he was once given something like a pigs ear for a treat, he growled at me when I went near to him, so I instinctively growled back (I am not saying that was the right thing to do, it just happened!) Then although I hadn't been going to take it off him, I did, very matter of factly with no fear (but again that might have been stupid when a largish dog with big teeth has just growled at you!), and whilst talking to him quite softly, but firmly. He let me do so with no protest whatsoever, but many dogs would not take that kindly, so I can't advise that as the thing to do. Also, luckily, it seems, ours has always been a far too big lap dog. He loved cuddles, and scratches and kisses, and still loves a little scratch, a few kisses, and always loves being told how good he is, and how much we love him.
Good luck OP, I am sure you will get some amazing advice on here from dog people who really know what they are talking about.
ps. Our labrador retriever has never shown the slightest interest in retrieving, but has kept his gun dog credentials in never being bothered by loud noises eg fireworks ☺