For one thing it's way too rich. Second, because it's revving super slow, it's barely engaging the clutch. That's my guess anyway. Instead of treating the throttle like a light switch, pull the trigger gently and hold it at a setting. I'd be jabbing it wide open and get the engine to rev up and clean out. If it just revs up and doesn't move an inch, look to your clutch or inside the transmission for faults. Is this truck brand new?