Well, I have Sims on my computer and on my boyfriend's computer. I created & played a family on his computer, but wanted to transfer it to mine... so I simply copied the whole save folder from: .../Electronic Arts/The Sims 3/Saves/. Then I popped it into the Saves folder on my own computer, and it worked fine.
I don't know if you meant that you want to transfer only the household, not the entire game save...? I'm sorry I can't help with that. You could just move the whole game save folder to your second computer, then start the game and copy the household to the library, if you want to play that household in a new town. If you copy the whole game save, that solves the problem with relationships/inventory etc as well.
To get the store content, simply log in at thesims3.com and download them again from your purchased items.