It isn't a bug Eric. If you chose to smash jars to get XP rather than absorb them so you can use a source spell that is up to you. At the moment smashing Withermere and the Joker seems to be the best bet. Give the Witch her one. That is 12k XP.
The other 3 you can do anything with - it doesn't matter. Probably kill the guys and then absorb but they are quite tough (level 7) now.
If you decided to buy something that is also up to you. I bought all the crafting things from Elder the Scoundrel seller (or whatever his name is) in the Sanctuary only to find you can't craft anything with most of them yet. Some were quite expensive.
You can always reload an earlier save if you find a bit that isn't finished or you made a mistake.
How source will work we don't know yet but in old builds it was too easy - you could remove your collar, step in a puddle and overpower anyone before you left the fort. You would not worry as you could get plenty of source points later.
Generally this was a good change but it has made physical damage characters a better bet than magical at the moment.
