Using the above example, on average you'd have a 3 in 4 chance to upgrade your item to [3][3][3], but I won't blame you for not trying those odds

I'm curious about the 50% chance of success and 20% chance to destroy, does your crafter not have a maxed out skill in Thermodynamics? Or do the percentages change at lvl 50? Come to think of it, what IS the level of your crafter?