Your pup should not be off leash until he has a solid recall down and even then, I wouldn't trust my very well behaved Loki to be off leash in front of the house without a lead/fence - nevermind other dogs, the idea of cars scare me too much! Also, if you KNOW your dog has that reaction to other people and dogs, even more reason NOT to leave him off leash. It sounds like you are setting him up for failure and he's learning some habits and socialization that is going to be tough to fix unless you start intervening immediately. Be grateful the situation wasn't worse than it was - you don't need a 6 month old puppy with a dog bite history.
I would suggest contacting a few local reputable rescues and asking them for advice on training centres/individuals and behaviourists. You may not find someone in your local area directly, but sometimes a bit of a drive is well worth the effort