There's absolutely no way you will ever get Kernel exploit on the firmware you're at. Your only option is to buy another PS4 or use this one for online play
It came out the box with an older firmware but once you update it you cannot go back. No matter what you do. So your only option is to buy another PS4 or use this one for online. Forget about PKG
You're probably missing parts of the file and they end up corrupted. Try using Winrar . Also download a small game to see if it can install without a problem on your ps4. If it does, that means its the games you downloaded that aren't valid