Hello, i'm no expert but here's the solution i was able to come up with (keep in mind it's still going to take a while, but it should still work):
-Boot into safe mode
-(restart computer then hold Shift until prompted to login)
Open Terminal
Type in this line :
sudo nice -20 softwareupdate -i -a --force --verbose
(sudo for privileges, "nice -20" for highest priority (probably doesn't change much but makes sure it's regarded as the top priority))
Wait for it to download (it started to slow down at some point then it would freeze at others but it was able to finish)
After this it should prompt you with an apple notification at the top right asking if you would like to restart your computer to install the update. Choose when you want to restart (i just selected restart) and it should install the update and reboot into the newest update
I hope this helped, this was the only think i was able to get to work for me
