Uh oh. I was all prepared to say how much I loved this little vignette when I noticed the continuity error. Seasons Greedings, the Christmas episode, happened two episodes after ToGoM. So if Lois is writing this thinking Clark is still dead, the whole Christmas thing hadn't happened yet.
Besides that, I did love the letter Lois wrote for her own catharsis. Only knowing you, I'm sure this letter will fall into Clark's hands eventually.