Few thoughts on this.... I currently have a 9.5 week old boy, so I KNOW what you guys are going thru.
BUT, as far as the person on the 4th floor... yeah, that's gonna make things a LOT harder. That's why breeder's will ask what kind of living environment a potential buyer has. You are going to have your work cut out for you. I would have strongly considered moving prior to getting a puppy. I'm not saying it can't be done - it most certainly can, but you are going to have to spend more time and have more patience with your puppy than most people will. This is not the dog's fault. The one advantage you DO have is the time of year it is. Man, so much better to be doing this in June and July than in January and February. My last pup was in the middle of winter for this and I just couldn't stand outside in Chicago and wait for her to pee any longer b/c I was freakin' freezing. And if I was freezing, you know she was cold too. So we'd go back inside and she'd promptly pee on my floor. You are going to have to make some big time lifestyle adjustments (I have to go sit outside for 1/2 hour waiting for the dog to go while my favorite team is in the middle of the Stanley Cup Finals - ouch).
And exactly as GMacleod stated (who IMO is an outstanding source of information) they will start to think you just don't want them to pee. I remember vividly my last girl going into my roommates bedroom and pooping on his bed! She just thought she wouldn't let me SEE her going. Even thru my mistakes, she eventually did *get it* and turned out to be a wonderful dog. I just expanded the learning curve in the wrong direction.
All I can tell you guys is that training them takes a few basic principles: #1 PATIENCE (took my last puppy almost a full YEAR to finally start putting it all together). #2 - Consistency. #3 Persistence. Feels like you've told them the same thing every day for 6 months and they just won't ever get it. But THEY WILL GET IT, eventually.
None of your dogs are abnormal, and none of them are dumb. This is all normal stuff and it's what makes having a puppy difficult and it's a huge reason why so many people should NOT get dogs (and I'm not implying anyone in this thread, just in the world generally). It's like raising a little kid but in a far more condensed time frame. So many people give up on them and this is why the rescue's are flooded with dogs that have to get euthanized.
My little guy is having his share of accidents as well, but not as much as the previous posters in this thread simply because we manage him more closely. He's gone 2 full days w/out going inside once. It's not because he's potty trained, it's because we take him outside constantly, and if he's not out, he's in his crate or I bring him up on the sofa with me to cuddle because they usually won't pee on you. When I know he just went, I let him run around in the house but only where I can see him, so I constantly have to get up, no relaxation!
Keep the end result in sight. With your persistence and consistent message he WILL GET IT. And after the *light turns on* you will have an unbelievable companion for years to come. Having puppies is tough, no doubt about it.