I worked at a chair for 12 years - in that time I've seen a lot of PhD students go through this.
If it helps anything at all: It's normal. At this point, you've already proven you're smart and knowledgeable. Now, the universe wants to see if you can also finish what you've started. That's the main thing a PhD proves: That you can take an incredibly interesting topic and then do all the boring stuff that they need you to do to be formally compliant with arbitrary rules.
Focus on finishing. Reduce the scope as much as possible again. Down to your core message (or 3-4 core messages, I guess, for paper-based dissertations).
If it helps anything at all: It's normal. At this point, you've already proven you're smart and knowledgeable. Now, the universe wants to see if you can also finish what you've started. That's the main thing a PhD proves: That you can take an incredibly interesting topic and then do all the boring stuff that they need you to do to be formally compliant with arbitrary rules.
Focus on finishing. Reduce the scope as much as possible again. Down to your core message (or 3-4 core messages, I guess, for paper-based dissertations).
Listen to the feedback you get from your advisor.
You got this!