Fitness, exercise and MY DOG...HELP!!! How do you do it :/

I would not rush to neuter unless you're seeing serious aggression issues. Yes, you will need to do it -- as someone said, we don't need more pitties -- but waiting until he's more fully developed seems to be the way to go to avoid future health complications. A gonadectomy will remove the source of hormones that are useful for physical development. The move to waiting longer for neutering is something that is changing over the last few years. I've lost a couple of dogs at a relatively young age to cancers that may be linked to excessively early neutering. I'm talking neutering that was done at less than six months of age.

At 9 months of age, your pup's training and socialization is the goal. You've gotten some good hints here, including a head harness, one of the most dramatically effective ways to bring a bouncy dog under control without using pain techniques such as a pinch or slip collar.

What breed is he? Is he neutered? I have a Bullmastiff, so I get what you mean by wanting to nip it in the butt before he gets any bigger. I noticed that right before we got Dutch (Bullmastiff) neutered he was maturing and wanted to mark/sniff everything. Once he was neutered, that was no more. Ote (Chihuahua) wants to mark everything though and she's an unspayed female. So I think it has a lot to do with that. She is small enough that she got the point of a few quick tugs of the leash and now she realizes that she needs to keep walking and not sniff/mark everything in sight. You may need a choker collar for a large, stubborn dog though. My best friend uses one on her English Bulldog which I was so against at first, and then she had me put it on my thigh and pulled. Definitely not painful, just annoying. Could be a solution.

+1 for Neutering and Puppy Obedience. Also do some one-on-one leash practice in your house, private yard or some place other than public spaces so that you can focus on your relationship with your pup, avoid distractions, and reinforce good behaviors.

I have fostered and adopted Great Danes, all with various temperaments. I've learned not to take chances with my dog or other people/other dogs. Last year I adopted a neutered male 7 year old, weighing @ 125# who likes to sniff and pee on everything, but at the same time can pull my arm out of my socket when he sees approaching dogs. He's one of the giants that I've known that will always need to be walked on a pinch collar and a short 2-ply nylon lead. When we are running, he is distracted long enough to keep pace, but he still makes a point of trying to meet other dogs (often in an alarming way). We just started walking at night when it's cooler and fewer distractions.

We have two bullies, and both are still learning to walk politely on a leash. Here is what I've learned:
1. When you use the head harness, they will hate it. One of my dogs ended up removing some of the skin on his nose trying to get out of it while he was with my spouse on the bike. He is fine, fully healed, etc, but he dragged his face on the ground trying to get it off. Neither of our dogs likes it, but both need it, and will tolerate it if they're kept busy.
2. Whomever told you your dog is too young for car rides is an idiot. You may, however, have a dog that doesn't travel well. You can talk to your vet about that. Also ask how long they can be running for at this age... it might fit into your plans (depending on how far/long you're running).
3. I would get him neutered. Whenever you decide, but it should be done. Even just to prevent him accidentally getting out and breeding more dogs. My heart breaks for all these dogs being euthanized because of how they look, and who their parents were.
4. Ceasar Millan's ways are not the end-all-be-all. Anyone who tells you that you HAVE to use force in order to make a power-breed respect/listen to you is full of *kitten*. My female dog responds well to a more disciplinarian approach, while my male dog shuts down if you raise your voice (or hand, or whatever). He requires a very positive training approach and responds best to food rewards. I personally prefer Victoria Stillwell's even approach to training, and recommend looking into her stuff over Milan's.
5. Look for a trainer who specializes in power-breeds. They understand the temperaments better, and will give you better practical advice. They're also more tolerant of bad doggy behaviour and will work with you to fix it.
6. My dogs have both been queued by "let's go". They know that they can't keep sniffing at this point.
7. Don't take your dog out any more without a secondary restraint system on him. I'm being dead serious - if your dog lost his crap and ran up to my dog (who is leashed properly), my dog would attack yours. She's not friendly with other dogs (she's an AWESOME dog, we just think that she has a dubious past, and was used for nefarious purposes). So for the safety of your dogs, and the other dogs who are on leash, DO NOT take him out without a secondary leash system until your training is sound. A fight will be extremely costly to you and to your dog, and can lead to behavioural issues in his future (ie. fear of dogs, willingness to fight, etc.). One bad altercation can take years of training, socializing and desensitization to "fix" a dog. Whether it's your dog or someone else's.

Your dog is a beauty, by the way!!!

+1000 for training and neutering.

i run with my dog and he is into sniffing and marking as well, but we have an interval based system that works really well for us. (i got him when he was 5 already and he knew basic commands but had always been walked off leash, i'm lucky though that he loves to learn and is very food motivated). anyway, our first five minutes is "warm up" time, during that time he gets his most urgent business out of the way and sniffs around, but when time is up and i say "ready, bronx?" he goes right into a run interval and keeps pace next to me on a short leash until i say "recovery", then he poops lol, then we repeat the interval commands. it's a good balance for him because he gets his time to sniff and explore during the walk intervals and he gets exercise during the run intervals. it works for me too because it's hotter than hell out and i like to slow down for a bit as well.

i have two pitbulls both tiny and runts. Luckily they are happy laying around all day. One of them is an angel on walks the other is a psychopath pretending shes on the hunt in the jungle ha. What helped me is a front lead harness foooor sure.

A disproportionate number of dogs in shelters are Bull variants. Here in the UK it's Staffs.

Partly it's because of the image, lots of puppy farms trend towards these types as they're easy to sell, but then people that struggle to handle them end up abandoning.

Fwiw I read something the other day talking about a trecento survey that highlighted far higher levels of aggression in toy breeds.