That is a beautiful dog. Beautiful. I mean it. You got yourself a damn good looking dog.

Thing number one. A tired dog is a good dog. Keep your dog well exercised and mentally stimulated and he'll be much easier to handle.

Thing number two. See what you can do about obedience lessons. With your dog's history, I'd actually recommend seeing if you can hire someone to come to your place for private lessons. Your dog has a past with other dogs that means bringing it in proximity with other dogs is a bit of a risk. Especially this early in the game, having him around other dogs is very much ill advised.

Thing number three. Keep up with the leash training and try to socialize but be super careful about it and do it in a safe, controlled environment. Hopefully it all works out well for you, but if it does, keep in mind, you can control your dog, but you can never control your dog. It is an animal with a mind of its own and no matter how obedient it is, there's always a risk that it will misbehave on a whim. For example, let's say you had your dog for five plus years and all this time it's never stolen food off the counter when your back's been turned. Then one day, when you and your buddies had friends over for potluck, it got into food and you're all like "Wow. I'm surprised he did that. He's never done that before!" Don't be surprised. He's a dog. He's gonna do dog things, including running away, barking, rolling in dead shit, on and on. Part of dog ownership is risk mitigation and knowing that dogs are as unpredictable as they are predictable and it's your job to predict and prevent unpredictable behavior. In the case of your dog, this especially includes aggressive behavior. He's already had one strike and a second strike would be tragic.

Thing number four. Seriously. That's a good. looking. dog. I'm jealous as to how handsome your dog is.

Thing five. We have a dog that is randomly dog aggressive. When I say randomly, I mean we can take her for a walk at the park and she's perfectly fine with 90% of the dogs she passes and one day she's completely fine passing up a dog and the next time we go, she'll bark, snarl, and raise her hackles at the exact same dog. In those circumstances, we control her, apologize profusely for her behavior, and immediately remove her from the zone of conflict. Dogs are weird, they have their own signals to each other, and by the time they're 20 feet within another dog they've both already made up their minds as to whether or not they'll want to get along. We use this leash with a sturdy chest harness that for some reason I can't find online any more. See that second loop? That's for you to grab with your other hand whenever you need to control your dog.

Thing six. If you need to avoid taking your dog out in public because it just can't handle other people/dogs/kids, whatever, that's fine and there's no shame in it. When you do need to take your dog out in public, say, to go to the vet, and you've decided that you need a muzzle for your dog (and I'm not saying you do, we're just talking hypotheical here) there's no shame in that. It's for other people's protection, you're protection, and most importantly his protection. You might get some funny looks, don't fucking worry about it. You're doing the right thing. Just know, if you do need a muzzle, your dog is gonna feel EXTREMELY vulnerable and you need to modify your behavior to help mitigate that.

Thing seven. You've taken a dog that has had a trouble past, given it a third chance at life, and you're ready to celebrate everything that is amazing and beautiful about it. Pet your dog. Rub its belly. Kiss its forehead and tell it how much you love it. That picture, right there, is of a dog with good, friendly eyes. It deserves every ounce of love you can give it. Love the shit out of that dog. If everything goes right, shit's gonna be AWESOME.

Thing eight. Experiment the fuck out of toys with your dog. See which ones he likes, see which ones he dislikes, and try new things from time to time. Sometimes dogs will like only one or two kinds of toys, sometimes all of the sudden they like completely new things.

Thing nine. This is my best advice (and I'm sorry for focusing on the negative, I'm just trying to give some tips to help you with your underlying concerns). My best advice might not actually be the best advice. Consult your vet. Consult dog trainers. Maybe even pop over to reddit and make a duplicate post for this over in r/dogs. I've gotten good advice from all three places over the course of me owning my giant ball of fun.

Thing ten. Seriously. I can't get over how good looking of a dog you have. Good pick.

Edit: someguyfromcanada, you've worked with rescue dogs before, right? If so, your input would be much appreciated.