How much can it take in? I haven't found a limit yet.

I think my highest carb day has been around 3000 grams, but that is a rare high carb day. If I am depleted, I can consume around 2000 grams before I spill over.
My typical high carb day is 400-500 grams, medium carb day is 200-250 grams and low carb day is less than 100 grams.
There are a lot of studies showing insulin resistance is actually worse in high fat diets (saturated fat diets) than high carb diets.