Set point for jams and curds is such an arbitrary thing for the home cook, at least it is for me!. Even with my sugar thermometer it is never exact. I use more successfully the cold plate/fridge method my mother taught me.
As you start place 2 saucers in the feezer. Once you hit the theoretical set point in your recipe (it varies so much from recipe to recipe) take the jam/curd off the heat and a chilled saucer out of the freezer and start testing for the set. Spoon a little jam/curd onto the sauce leave for about a minute – I put it in the fridge if the kitchen is steamy and hot – then push your finger through the jam if it wrinkles then it’s done with curds you’re looking for a straight line through the mix that holds for a bit, a parting of the Red Sea sort of thing. If not return jam /curd to the heat and keep cooking and try again in 5 mins. I rinse the plate and return it to the freezer.
In theory jams need to reach 105C and curds 82C with a sugar thermometer.
It’s not an exact science, trust you instincts and how you and your family like their set. We like ours softer set some like it more firm and that is the beauty of homemade you can have exactly what you want.