I think it should be 48% of median wage in state. That seems to be where the benefits are the highest. Maybe there should be an alternative of 7.25 in 2008 dollars adjusted to 2018 and for each years subsequent inflation. That would be 8.75 an hour in 2018. The greater of the inflation adjusted minimum and the 48% of state median should be used.
http://www.governing.com/gov-data/wage-average-median-pay-data-for-states.html
A state like Florida would have a minimum of 8.75 because it would otherwise be under 8.
Colorado would have 9.18.
New York would have like 10.10.
Either that or a national of 10.10 would be good.
70% is usually the point where people start not being employed to a significant extent.