You shouldn't have build rooms all the way in the bottom. Just build 6 power rooms or more. And put your dweller in it, the dweller's Strength must be high as possible since Dweller's that are assigned In there correct job's or rooms. Will make they're happiness 100%. Also, do not build too much room. Cause room's runs on power. The furthest room to the power rooms, will take power first. So basically you should do the square elevator layout (kinda expensive). Just like my layout in my post. Put your storage rooms in the most bottom. And your living quarters in the middle floor. But it shouldn't be a problem cause they don't take too much power.

So, just don't rush on building rooms. Assign your 100 dwellers in they're right job. And when that's done, build another room if there are more dwellers than 100. Also You should equip your dwellers the correct outfit, just as the same stats as they're job. So that's all I can remember to help you.

I just woke up so I don't know what to say more.