Daisy, here is a recipe I follow which produces really nice apricot jam:
Apricots 1.28 kg
Sugar 1.28 kg
Water 1 cup
Lemon juice 1 teaspoon
Simmer stoned and halved apricots in water. When soft add sugar, allow to dissolve and boil on "high", stirring continuously with wooden spoon until set. Add lemon juice and boil for 1-2 minutes. Add to jars immediately and allow to cool before sealing.
I have found that adding a teaspoon of brandy to each jar when the jam has cooled prevents any mould developing.
I wonder why your husband's jam is not setting. I have never had a problem with apricots but have had with strawberries which are low in pectin. Is he not boiling it down enough? Did he use a jam thermometer? To check if a jam has set I use the cooled saucer technique. Cool a few saucers in the fridge, then when you think the jam has thickened sufficiently remove about half a teaspoonful, place it on a saucer and leave in the fridge for a minute or so. Take out and push the jam gently with the side of a finger. If it has set it will have formed a thin skin on top. If not continue to boil and check again every minute or so.
Our big apricot tree seems to produce a bumper crop one year and almost nothing the next. This year is a lean year, so no apricot jam.