This letter is the purest fantasy and is written for nothing but the humor.
We don't have a still, never had one. Jack was a rabid teetotaler.
As for the mosquitos, I've heard lots of "I met a bigger mosquito than you did" stories, mostly fantasy (including the one about the guy at the Alaskan airport who accidently refueled one at the end of a long shift) and I can assure you that this not the way mosquitos are.
Mosquitos do not carry off prey, instead they land and suck blood. They're insects, generally no more than a half inch across at maximum. They lay eggs in pools of stagnant water which are not usually in trees. Etc.)
This letter was written to Pete Buckton, who was a grandchild of Dill Royle Hansen.
Jack Chisholm was a scoutmaster for the Boy Scouts at about this time, and it sounds like Pete Buckton was in Scouts as well.
Jack did have a broken foot about this time. He limped a bit for the rest of his life, even after when wearing the special shoes he had to have made for his foot.