Hope you all remeber me lol. I have a 5 year old lab X GSD I think he has more GSD then collie, he's called Bob

Now he weighs about... 30 kgs and my god can he pull when he wants to . He can be very reactive with other dogs, we normally have pulling, barking and lunging, if the dog he has spotted is on the other side of the road walking the other way he will quite often stand up on his back legs. He doesn't like crowds, bikes, or strangers, which can be hard as when hes walking they always seem to stare at him almost.. which doesn't help.. cats are always fun to chase! You cant beat going for a drag! Litrally! If any wildlife is in the garden he will have to run out and chase it all away and sometimes put in a bark or two. There are a few people who have said how they are very pleased we have still kept him. I think if we had taken him back he wouldn't have left the rescue and i imagine would be PTS. We did use to go to a trainer, but my dad didn't want to pay the money anymore as he thought it wasnt getting him anywere. My mum wants to but right now we dont have the money. Though when we was with the trainer she did say that he is protecting us.
So we have a large 30kg dog who is fearful of other dogs, using agression to protect himself, and he 'has' to thing about protecting us aswell! He has been attacked twice while on his lead and once off. He's always on high alert while were out walking or if am watching tv in the lounge and he is lying down, if he hears a door shut, his straight up at the door barking. That goes for when people walk past infront of our house and even when there on the other side of the roas. If theres a dog then he will happily stand on his back legs and scratch at the glass ...
I dont think until we can ... whats the right word... Well until we can crack his protectness over us he wont really improve around other dogs. i dont mean in a big change or anything that might take months, years, or it may never happen but its means we have tackled one of his problems.
The sad part is he loves to play fetch and run after his tennis ball. But we cant take him out that often to run as the fields near us are all open and I cant risk a dog fight.
Though I do let him run there is a smallish field near us that is fenced in I always keep him on his long.. 30ft lead but I only hold onto it when he spots a dog even then I fed him. But if it wasn't for me he wouldn't be getting a run at all.
So does anyone know how we can start to deal with his protectness?