Hi Danelle,
Those are all great questions. First, there is currently no Disney PhotoPass app. I'd be thrilled if there were one!
There is no direct mechanism to upload photo to your PhotoPass account wirelessly. You can import pictures to your PhotoPass from your computer or via a
Facebook uploader. As a wireless work around, you could try to upload pictures from your Facebook account on your phone or tablet. I haven't tried this myself, but I believe it would work.
I called Disney PhotoPass for you (407-560-4300) and found that there is no limit to the number of photos you can import into your account.
You may want to check out the very informative
"Help" section of the PhotoPass website, which answers many of the technical questions you may have about the PhotoPass process.
The independent website StitchKingdom.com has a section called the "Definitive Guide to PhotoPass" which is also extremely helpful in understanding the ins and outs of using PhotoPass.
Good luck with your planning. Please let us know if you have additional questions.