Divorced in 2018. Ex and I rec'd a state tax refund that was split 50/50, but the 1099-G I received was for the whole amount. Do I claim it all or adjust to 50%?

If you did not itemize your deductions in 2017, you do not have to report any of the state tax refund.

If you and your ex-spouse itemized, then you would report 50% of the state tax refund on your 2018 income tax refund.