First off, I want to say that I am no use when helping PS4 users (so I apologize), as I use an Xbox One. However, this seems like an Issue with your connection or PS4 or possibly the PlayStation servers rather than the game. Have you tried installing any other games/apps? Maybe the same issue happens with any other installation? If so, this is the PlayStation Servers that are messing up. I recommend you report the bug here or wait until the bug is patched.
If you have a wireless connection, are you making sure that no one else is installing anything and also making sure you have a fast, active download speed?
I think the best idea is to leave it to install even though you said this didn't work. If you don't want to attempt that option again, the only other option I can think of is to report the issue, then try installing the game again. When it stalls, pause and unpause to make it reach the 98-99% stage. Then leave it unattended and see what happens.
If you have done that already and it didn't work, I'm sorry for not helping and I think it would be best to contact Sony Support or our Community Manager LilTrashPanda.
RAD and Deformers has been going through quite a lot recently and they are trying their best to fix it.
Let's just hope your game eventually installs.