Select text all the way to the end
Is there any way I can delete the text from a specific point of my text frame to the end of the text (including the text in linked text frames)?
Yes, indeedy! A close inspection of the InDesign Keyboard Shortcuts Chart tells me that Command/Ctrl-End moves the cursor to the end of the story, even the end is a hundred pages of linked text away. Just add the Shift key to get Command-Shift-End (or Ctrl-Shift-End) and you’ve just selected from any point in the text to the end of the story. Then you can cut it, delete it, or whatever you feel like doing with it at that moment.
Here’s one more technique: Use the Story Editor. Place the text cursor in the text frame and press Command/Ctrl-Y. That opens the story editor window and places the cursor in exactly the same location in the story. The Story Editor lets you see and edit the entire story, no matter how long it is, and even if it’s overset (won’t fit in the available number of frames).