Can you tell me what you changed so in future I can fix it myself?

Now that the first issue is fixed let’s try to fix the others.

My first comment:
2)Sometimes the go-to cart popup will pop up on its own and won’t have any content in it

The issue is still present.
The problem is that it is harder to replicate. The best way I found is to go into incognito and walk around the website, if nothing happens close incognito and open a new one. Sooner or later you will notice the empty popup with a black square.