Restoring the original Touchwiz apk after a massive screwup xD

Hello everyone =)

I've been having this problem for a while with no apparent way to solve it...

I'm running a stock non rooted Lollipop on my Note 3. A while ago I saw a Note 4 launcher and got excited to install it. So I installed the apk file overwriting the existing Touchwiz. I figured that if it doesn't work I'll just go to the "uninstall updates" option to go back (been doing that all the time on my old Xperia S). I started getting the "Touchwiz has stopped working" message over and over again so I went to the "uninstall updates" option and found it greyed out. I deleted Cache and data, tried to reinstall the older apk, even tried to install other apks but I just keep getting "App not installed". I tried reflashing Lollipop using Odin but it still doesn't work!! xD

I have the original apk file for the launcher. Is there a way to fix this that doesn't require root?? I'm desperate here xD

Thanks in advance!!!!!!! =D