I started a hardcore Snowball Earth game with Icy starting temp about the same time as your post. I did starve my first go, death by bear the second attempt, but now in my newest world I feel very stable. Bear, foxes and the TRADER are the most stable food sources. Carrying 2 spears makes it easy to dispatch foxes but bears are a challenge unless you carry about 8 spears and build a quick 4 block tower to "hunt" from. Hares are a rare find as well. Your first days is to raid as many visible ruins as possible (while walking) to get food and foraging materials like reeds and grass. Also you want to explore and hopefully find an Agriculture trader. Once found, best to set up camp close to the trader and trees and off the glacier of course. I am working to make a greenhouse now for carrots and turnips which should really cement my food needs.