hook grip on DLs sucks at first. my recommendation is to practice on chins and other rows to get reps in and gradually work your way into doing the heavy stuff. your thumbs will hurt.
and on that note, doesn't look like you are really adhering to the internet-standard of balancing pushing and pulling for your torso and arms. i remember years ago reading eric cressey saying that reps should be balanced always between pushing and pulling exercises, and the planes of movement should also be balanced. if you're going to be unbalanced, better for it to be on the pulling side. in one form or other pretty much everyone i've ever read backs that up, and it makes intuitive sense.