He wouldn't be worry, he has been calling Spence Jr for quiet sometime now and is eager to face him. And this will be his perfect opportunity, no more Bob Arum in the middle for him to negotiate with Spence Jr and PBC. He might get the short end of the deal, but still, that money is going to be big.
Exactly, 50% of 10 million is smaller than 40% of 20 million, so the percentage does not really matter and Crawford has to take a low percentage for this fight to finally be sealed. Spence is a PPV attraction, so if Crawford could beat Spence, then he will become popular and next fight of his will make him earn more.
That's why Spence Jr. is called the king of PPV because of the revenue he can attract through PPV whenever he got some fights. For Spence, I think he will be more than happy to accept that 40% purse cut just to make the fight happen and that specific cut is already big enough for him as he's now flying solo with no Bob Arum.
He may be under Mayweather Promotions in this fight but his cut will be much bigger than he's with Bob, and that will be his biggest paycheck in his entire career.