Forgot to give the sources for the Finnish casualties not easy ) : Jari Leskinen and Antti Juutilainen :Talvisodan Pikkujattilainen .
I put this book out a couple of years ago. I combined two reports that General Erfurth had written for the Historical Branch. They might be of interest, as Erfurth was the OKW liaison officer to the Finnish HQ. https://www.amazon.com/Last-Finnish-War-Waldemar-Erfurth/dp/0615969593/ref=sr_1_4?s=books&ie=UTF8&qid=1466700270&sr=1-4&keywords=erfurth
I bought a couple of years ago a book By a 6th SS survivor. I think that could hel although 50% of the book is about taking part in the Ardennes operation.
That sounds like Zoepf's "Seven Days in January," but it was south in Alsace, not the Ardennes. Good book, though!
What's truly sad is that the incompetent Soviet general who disastrously led the Soviet forces in Finland was relieved of command and placed in charge of the Leningrad defenses. No surprise that that too ended in misery for so many. Veroshilov was truly a sorry excuse for an officer but a die hard communist which is why Stalin kept him around. He was also the main culprit behind Tukachevsky's fate