Due to the Corona crisis I currently dig out all my old equipment, clean it and look at every detail, test the rain proof jackets and so on. Often I throw it afterwards into the dustbin.
I was told it before, so my financial disaster isn't so big: Mainly the real issued military equipment survived the decades. Nearly all civil equipment fell in pieces just by aging in the wardrobe.
I am not yet through it all. But I already tend to say, that stuff without NATO Stock Number usually isn't worth the investment. If it's as cheap as the Solognac equipment the calculation is a bit different of course. But I also owned pretty expensive civil stuff which fell in pieces after 10 to 20 years.
Only civil high end equipment like my Hilleberg tent looks like new, Ortlieb bags and pure Cordura nylon rucksacks look like new too after decades.
I think that the fabric you show us in the photo was coated. Probably it was a polyurethane coated polyester fabric.
After round about 10 years in the storage or in use the coating falls off.
If this happens in the storage you see it. But if this happens in use you don't realise it. Suddenly you discover that your stuff sack isn't water proof any more. You can blow through a former waterproof fabric.
Now the threads aren't glued together anymore and they fray out.
In a more complicated constructed like your pouch this happens at first with the fabrics that are thinner and often bended and folded. But the others will follow immediatly if the other fabric comes from the same factory.
In my experiance such stuff can not be repaired successfully. The problem will continue in the next corners pretty soon.
I would throw it away instead of investing my time in it.