I've been curious about 0 speed players myself. I've seen post that said it doesn't matter and they aren't that slow but I've never kept them or played them on my teams.
In that post about the 0 speed players, it was said that 0 speed players were the slowest players on the field, that's all. I have a linebacker with very little peed that still plays well. I think they make up for the speed with other attribute. Your DE seems to be a very good run stopper.