It probably downloaded and installed part of the update, then you disconnected it, so you have a phone with a totally corrupted operating system. Bring it to a Best Buy (unless there's a Samsung office near you), and ask them where the Samsung desk is. )Most Best Buy stores have some Samsung people working there, near the cellphone area.) They can kind of "force-feed" the old OS (or maybe even the fixed 4.3) into your phone.
Hint - don't try to get your phone to update. Wait until it ask you if it should. The carriers dole them out to a few phones at a time to prevent just this sort of problem. Try to send updates to all the phones on your network at once and all you do is crash the entire network.
Information - your 30mbps wifi is 30mbps from your router to your provider's office (that's the only piece of the internet that they have any control over.) There's no way to know the speed from there to the server the update is coming from, but if it's 2kbps, that's what it is. (Some commercial servers have gotten so overloaded at some times - like CNN's during Earth-shaking news or Quicken's on one April 15th - that they just stopped entirely. If tens of thousands of people were trying to download the update when you were, it could have taken weeks, if servers aren't built to drop connections before they crash from overload.)
