It's sounding to me like the top of your list based on your current situation and preferences might be the Dogue. The Newfies and Leos probably aren't going to live the longer lifespan that you're looking for. I don't think I've ever seen a shar pei without extensive health issues. And if you have to wonder if you could handle a Boerboel, you can't handle it. I haven't owned one, but I've worked closely with a couple. One from puppy to adult and the other as an adult. I wouldn't recommend them to a household with other dogs. They can learn to tolerate other dogs if raised with them, but in my experience they really only tolerate. The family that raised the boerboel puppy ended up keeping their other dog largely seperate from him because even though he was raised with the dog from puppyhood, he just did not want to interact with it.
From what I've seen, the Dogue has mostly just basic big dog issues when it comes to health, can live a decent life span if well taken care of, and is laid back enough to get along with other dogs and for a moderately experienced handler to do well with it.