I watched the video you referred to and the actual specification given was a minimum of 90° and a maximum of 460° from hand tight.
Since you are at 4:00 you will need to turn your flash hider 420° in order to line it up properly, which is still within the required specs.
As far as the hand guard cap is concerned, that simply slips over the barrel and is not directly attached - although it is probability pinched between the stop shoulder on the barrel and the front sight base. You could try turning it with a rubber strap wrench that can be found at the local hardware store. I don't believe it would take all that much force to turn it, but it's your decision if you want try that or return the barrel / upper assembly.
Best of luck with your project.