I'd do what Pat suggests and just clean it out, if it's that bad. If you can't do it all at once, clear some out every night for a couple of nights. Sometimes these things happen at times that aren't all that convenient.
If you decide to wait, in addition to stall additives, I'd add more shavings. As bad as you describe, probably a lot more shavings and stir it all in.
It is hard to gauge how your litter management is going in a freezing coop, especially the first winter. Everything freezes as you go, so you can't tell if you're adding the right amount of shavings or not. Then you get a big thaw and find out you didn't add enough shavings and it's too wet and stinky. For next winter, now you know that you need to increase the amount of shavings you're adding to the coop as maintenance. You may need to be adding more at one time or the same amount more often, depending on how you decided to manage your deep litter. I didn't manage my deep litter perfectly the first winter, either. I did a lot better the second winter.