jj i think you are thinking about speed wrong. its not like in HD, your player can be so fast the other team can't keep up with him. i am pretty sure that HD calculates "abilities" of players. so the guy defending your guard, they take his ath and def (primarily) and then a host of other factors, and come up with some defensive score, that gets used against your offensive score. so just having a speed advantage tells a very small part of the story, IMO.
you also push your players for a lot of minutes. thats fine, probably smart, as you have a huge talent gap from starters to backups. but its going to result in a poorer performance than you would expect from those guys, playing with real backups. also, you are running slowdown. all in all, you simply have to expect lower fg% if you are not running normal tempo than if you are running normal tempo. im not saying you shouldn't be running slowdown, just that, between slowdown and the fatigue, you have to expect lower performance.
i agree with previous sentiments that hurd should be a bigger part of the equation. not a starter, though. something just feels off about your team, i just can't place it, maybe its just overall performance degradation from the fatigue and slowdown. why don't u try moving him to pg and see if that helps...