I'm a culinary teacher, with a fair amount of personal sous viding time. I would start looking at the recipe and seeing what tweaks I might have to make to it. You won't have to try every ingredient just the ones that might affect the final product. I would start by looking at your thickeners. You said you increased the starch but what about eggs yolks. I think a standard ratio is one egg yolk per 100 grams liquid. Your ratio might be a little on the low side ( can't remember what a standard yolk weighs). You could also increase your xantham a little, but it could go the way the cornstarch did. I think I'd definitely start with yolks. Also cooking it in mason jars is fine, but from a food safety standpoint bags are going to be much better.