I am new here and have been a student of traditional Japanese silk embroidery for over five years. The most "simple" repair requires hand dyed silk (imported from China or, as I prefer, from Japan) and framing the piece for correct tension. This may be simple in your estimation... but not. The creation of many of these old embroideries requires/ed specialized skills, but even more, specialized tools and equipment. I'd be glad to send you pics of my work and if I can help please DMail. Regardless of what you do with your runner, the piece is a treasure and should be stored or repaired accordingly.
While I cannot repair your pc. I did want to say it is beautiful and I wish you luck. A few years back I joined an on line sild embroidery forum. It has gone out of business. They would have a new project each month and you would join the project. I really enjoyed it. I no sooner bought some new ribbon and that was the end of them. Anyone know of another forum such as that one? I'd certainly like to know.