I typically wear 9.5 in an open Teva sandal but a 10 in a closed style. I tried both in the Ewaso & kept the larger, BUT I wanted to wear with socks post foot surgery & for excursions. I machine wash them in warm water & air dry without any shrinkage. You can adjust heel & top strap size, & the toe box is roomy. so I would try the 6 rather than go up to the 7.
I don't have this exact model, but I have 3 pairs of Texas and they are all amply sized. I'd go with the 6.