Welcome mmgsport! Sorry I have grown jade plants but not for years and years!! I think you may be correct in thinking its bugs - there is a root mealybug that is harder to get rid of and I think its also harder to ID on the plant.
JC I would agree with you that a deep pot watered regularly even in colder temps would cause rot. Sorry that I'm not more help!! The only jades I've ever seen that have thick trunks are older plants, which do come available from time to time - especially through local succulent and cacti societies!! Good luck Mmg!
