"Wrap in furs" has at least one benefit: it can keep the character warm even if the temperature is such that you'd wake up shivering halfway through the sleep without them.
Spoilage is randomized. It seems a spoilage roll is made at the turn of every day for every item subject to spoilage, with different outcomes for different stacks. The roll is influenced by temperature and cellar storage. It makes logical sense and I don't think that's too detailed to be an issue for JEB Davis. Sometimes you can get unlucky to have things degrade almost immediately, and sometimes they can last a fair bit longer than expected.
A bug/exploit/feature is that things don't seem to be subjected to spoilage when your character is away, so it's possible to go away on a two week trip and then return to find that the raw meat left behind in the cellar hadn't spoiled (I tend to leave raw meat to either spoil or be used for cooking a bit at a time, as dogs can eat spoiled raw meat, but not spoiled cooked meat, so if it spoils it can be used for dog food).
I haven't hired any companions with the new capabilities yet, but in the past I hired them only for the game course event and for robber quest posse collection. Those that died were given a fire burial (which is a pain, as leaving the site blocks the burning process to complete correctly, so you essentially have to sit around in the area through the process, rather than return to the village where you left your cow of burden to collect it so you can bring home the spoils).
I've never encountered the same foreign merchants twice: they're always shown as nameless when looked at (if you return to the same group during the same trip they're known, of course).