I had a go at your TGD, typerextreme, and changed some settings. Most importantly, your population area is much too big. No wonder it takes ages to populate. You should copy coordinates somewhere in front of your view, paste the into the area, and then try no minimize the area lengths, so the pop falls within your view area. Take a look from above and you'll see the boundaries and your camera.
You wanted snow on the trees, I changed it into my method of getting this, with a distribution shader. I reduced the tree size and decreased the distance between trees, and distribution up the mountain (differently, you'll see).
Now you'll have to import your tree again, and don't take notice of the mistakes that happen when opening the tgd (I work in a different build). Just import your tree, save and reopen. That should work.
---Dune