Upgrading from 8.1.2 to 8.3 via IPSW Bricked 6 Plus.

By bricked I mean, I can get the phone into DFU mode but as soon as the restore starts my phone gets stuck in recovery mode.

I have 6 plus that was on 8.1.2 I downloaded the IPSW for 8.3 (the corrects 6 plus version)and tried to install it via option+restore, I got error 14. I couldnt download through iTunes because of slow internet, it kept timing out. Phone bricked and has been ever since my first attempt to restore/install. But i don't always get error 14, sometimes the phone freezes on the restore progress bar for hours.

iTunes is updated. My laptop has not been updated to 10.10.3. I have extremely slow internet and whenever I try the download through the App storeit fails, then it starts from the beginning when I try again. I was able to download from the Apple website (not the combo update) but when I tried to install i get a message saying "OS X Update can't be installed on this disk. This volume does not meet the requirements for this update". My mac is currently on 10.10.1.

Sometimes it hangs up very early in the process. Most of the time i get error 14, sometimes I get error 9. I have also tried this on the windows side of my laptop using VMWare and also got error 14. I'm in Afghanistan with no access to an Apple store and sure they may send me a replacement but that would take 10-14 days minimum so I'd like to exhaust all options before going that route.

Would updating to 10.10.3 make that much difference?

if so, whats up with the error saying it can't update the OS X?

would downloading 8.3 from iTunes make a difference?

Thanks for your help.