That is not normal. I’ve had projects with 10k words per doc open very quickly. I didn’t try that many footnotes, though. I know some others use a lot of footnotes.
I would first try re-indexing your project (Under File -> Save and Rebuild Search Indexes). This may not help.
If your document is directly inside the Manuscript/Draft folder without another level of folder, that can cause some issues. So if that’s the case, put the document inside a chapter folder and see if that helps.
If those don’t work, I suggest copying your project from the binder (select all) into a brand new project (Drag and drop, not in to the Manuscript folder, but into the binder root (and then move the files around). Sometimes an existing project starts behaving strangely for no known reason. Copy/paste into a new project often fixes those issues.