The stress_mod issue likely means an error created while editing save files, as I am not aware of any changes in the mod and the error points to vanilla content. Hopefully you can undo, or have a backup of that save file. Though it's not hard to add it back to the stats dictionary with default value of 1, but if they are still present then the issue is a typo somewhere else.
restraintype should be apart of the expandedfarm dictionary inside the state dictionary. These are the default values, adding any missing should bring save file up to date.
var expandedfarm = {restraincattle = false, restraintype = "none", bottlesprice = 10, bottlesowned = 0, storingpiss = false}
String + Nil for Mansion.gd:690 is a derived error.
The following line appears to be wrong(Edit: expansion.gd:2208): if farmmanager.jobskills.farmmanager == null:
It should be: if farmmanager.jobskills.has("farmmanager") == false:
Nil > int for Mansion.gd:1238 is also derived.