If Soy Milk gets congealed at the bottom, is this a sign that it’s going bad

Have you ever put a quart-sized container of plain water in the spot where your soymilk froze? Perhaps that spot in your fridge is actually very cold--not cold enough to freeze milk with all its fat content (even skim as some), but enough to freeze soymilk (especially if it's settled and separated a bit).

If the soy is "sweetened", I would not suggest using it in a savory sauce. However, if it is unsweetened, it should be ok. I personally like soy, but it all depends on the brand, and whether full fat, sweetened, plain or vanilla as to how I would use it. You might try baking with it, perhaps muffins, cake or biscuits - and substituting the soy for whatever liquid you would otherwise use.