Trees, Shrubs and Conifers: Seekin opinion about a potted fir transplanted in the garden, 1 by Elgyn

Elgyn wrote:
I have a potted Christmas fir I bought..silver fir i think. It stayed inside for a lil over a month…half of the time in a colder place, a porch without windows. I waited for so long cause the weather outside was awful around -10 celsius and I didn’t think its appropriate to plant it then. When a more mild weather came in February, the needles were already to starting to fall off. As I took it out of the pot, I saw that the longest root seemed to be severed and the end was starting to get slippery..probably they severed some of the roots to fit the pot better, something I didn’t know they do:(
I know I made mistakes, but I don’t for the tree to pay for them. Could I help it any way to survive if there is still a slim chance? I watered it every 10 days while in the pot. And I plant it in a sunny place, with soil for pine trees and straws on top to protect the roots from the cold, but it continues to die:(
If you tell me ur opinion I'd be most grateful