If the chlorine you bought was really fresh it could have been more potent than 10%, or you could have had a testing error prior to adding the chlorine. Tabs add chlorine more slowly, so unless the tabs that were added have already completely dissolved that is probably not the source. By the way, you can remove the chlorine tabs and let them dry out and throw them away. Also husband doesn't have to agree to read up on TFP, but you might ask him to let you continue to take care of the pool until y'all decide if this is the pool care method you want to use going forward. Trichlor tabs add CYA and you don't want that level to get too high.
I just noticed the SWG in your signature. Is it turned on? If so that could be where the extra chlorine came from.