Re: Brook v Khan - How would you split the purse?
You have to ask yourself,"how likely is it that this fight will happen anytime soon?" Not very IMO, the seeds have started to be sewed, though.
If the fight happened tomorrow, I'd give Brook 65 Khan 35, because Khan needs Brook more than Brook needs Khan, at this moment in time anyway.
If your scenario were to come true, although I think Khan will fight McCloskey first, then a 50-50 split would be fair, as I'd expect this fight to be big bucks and Matchroom with Sky, bringing more to the table.