just a suggestion that i find helps, particually with recall, have you tried using a clicker? clicker and reward system is great for food loving doggies!
a really brief explanation….
you call your dogs name followed by command eg doggy ‘come’
as soon as he looks round and starts to move towards you CLICK and when he gets to you give him a tastey treat. he will learn the click noise means he is going to get something great. this will help strenghten his recall giving u more confidence with off lead exercise.