1-a Follow these instructions: iTunes for Mac - How to copy purchases between computers: http://support.apple.com/kb/HT1373
1-b You can use or sync your purchases from the iTunes Store on up to five different computers (these can be any mix of Macintosh or Windows-compatible computers). When you sync or play an item you've purchased, your computer is "authorized" for purchase using your Apple ID. Or you can use the iTunes Store menu > Authorize this computer. You can authorize a computer with mpre than one Apple ID. You can disable the automatic downloads by reversing the steps taken to enable them. See Tunes Store: How to enable Automatic Downloads, http://support.apple.com/kb/HT4539 mmOjn yopur computer, uncheck music, apps and books in iTunes > Preferences > Store. On the iPads, go to Settings > Store and turn off automatic downloads for music, apps and books.
2. Try the suggestions for Apple TV (1st generation) may not play content purchased from the iTunes Store, http://support.apple.com/kb/ts1359
I'm going to slightly disagree with Jim and suggest that you not sync the content on your laptop to your wife's laptop. It might cause more difficulties in syncing than you want to deal with.
Instead I'm going to make the suggestion that you find a reputable computer shop in your area and just upgrade the size of the HDD.