Your beer's almost certainly not suffocating. How are you measuring your temperature. Maybe it's just the fact that you're now controlling your temps (meaning you're now correctly fermenting cooler) that's making the yeast seem sluggish to you. The cooler the temps, the more "sluggish" your fermentation could appear. Also, depending on how you're measuring/regulating the temps in the freezer, maybe things are way cooler than you think.
Thanks for the reply. I'm using a two stage temperature controller to manage/monitor the temp. I tape the temperature probe to the outside of the carboy and then wrap a fermwrap around the carboy and plug in both the fermwrap and chest freezer in. I've fermented both beers at 68F with a 2F differential.
Before I used the chest freezer, I controlled my temps with a round refrigerated "wine cooler." The only difference was the neck of the carboy stuck above the rim and I fasioned a piece of plexi-glass for a top with a hole cut out for the neck of the carboy to stick out. It works quite well and I still use it but wanted more fermentation space and couldn't find a cheap wine cooler anywhere.
I'm pretty confident the temps are correct, but the chest freezer is the only item I've changed in my process with the exception of some new better bottles which I have used before so I thought it would be a point of focus until I could rule it out.