Now that your baby is 12wks old there is no reason why he can not hold it for 3 to 4 hours. I would not give him all that room to play in and use the bathroom. Crate him in a crate that only allows him to turn around and lie down. He needs to train his bladder to wait till you come home to take him outside. I got kobe at 12wks and after a week of frustration, I finally crate trained him. He would be in his crate and knew he had to use the bathroom after getting out or I would put him right back in there for 5 or 10 minutes untill he finally would go outside. He would go on floor if I didnt make him understand he had to use outside potty after being in crate for a few hours. He has always held it over night so I knew he could do a few hours in the day as long as there was no room to use the bathroom. when at home if I could not be with him every sec he would be in his crate while I was doing chores or cooking. He never whined and just watched me. Of course the only way they learn is by making a potty mistake at which time you catch them and tell them outside. But with you living in a condo you may have stairs to deal with so that is a big ordeal. I have never dealt with owning a pup in an apt. I know petco has this fake grass pad and it is suppose to be easy to clean, you may want to try that. and if you have a closed in patio place it out there so he will always know outside is to use bathroom. If not closed then leash him to potty outside on it or even pee pad.. Being consistent is the key. and it can be hard, but you are the boss and if you dont show him this then he will show you he is.
The Pet Loo Indoor Yard Training System for Dogs at PETCO
I also found out that as soon as I taught Kobe tricks which I started at the age of 14 wks or less, he started doing better with potty training cause he realized that doing something good gets him a treat, which was just his kibble but prasing him and rewarding him made him easier to train either potty or a trick. Good Luck.... it will get easier but be consistent everytime.
A good teether might would help with his energy. The bully sticks are great to keep them entertained and they are natural and last a very very long time. Kobe loves them.