Extreme leash pulling

[Whistler's mum]

My year old black lab is an absolutely wonderful dog, except on a leash! I have been to dog training with him which calmed him for a while but after three months, he still hasn't learned. I am currently walking him using a gentle leader harness but he can still pull considerably on this and has open sores behind his front legs from pulling. I have also tried a halti head collar which seems to work miracles with other dogs but unfortunately, my guy scratches madly at his face with significant bleeding gashes as a result.

I'm starting to lose faith as there are limited and unappealing off leash parks in my area. I really want to be able to walk him on a leash with my other more well behaved dog and get my life back.

Anyone in a similar position?