I would bring the giant clip in, double click on it in the Project Panel andset an in and out points in the Source Monitor. Then go to the top of the interface clip/make sub clip. After you name it it will appear on your project panel. Repeat the process for the sections that you need.
I’d have Media Encoder installed on your machine.
Then select the sub clips, right Click and Queu.
Media Encoder will make clips of those sections that you can bring back into Premiere without the giant clip.