Mel,
I really dont have any tips...
Does Jacob have a ball, one he can throw outside? maybe if he throws things get down (as best you can with a baby belly) Tell him we dont throw etc, then take him outside & tell him he can throw this ball outside, but we dont throw stuff inside or something similar??? Would that work or would that just confuse him, about what he can & cant throw & where etc?
I used to just remove the food if Maddy had thrown it & did as you say tidy her up & let her out of the high chair & let her go play, but then tell her she couldnt have a biscuit or her meal now as she had thrown it & right now was not meal time... She only threw it about 6 or so times so it wasnt too bad...
I really dont know..but hopefully someone else has an answer for you...

Good Luck sweets your doing an amazing job!