Since we are now divorced, can one take the standard deduction and the other itemize using the full value of all of the deductions?

Were you divorced before or after 12/31/17?  If it was after, then no.

We were divorced October 2017, so he is filing single and I am filing head of household

OK, then if one of you wants to take standard deduction and one itemize, no problem.

And I don't have to split the deductions or take only 50%? It seems it would work for both of us, since if we had to split the deductions, neither of us would have enough to exceed the standard deduction.

Well, you can split the deductions as long as they total the deductible items.