Go to the last evidence of blood and circle it, with the circles getting wider every round. Look carefully before you take every step so you don't step on any sign. Take some flagging tape with you so you can flag every spec of sign you see. (we're talking hands and knees tracking) Do this even at the beginning of the large sign so you can look back at your trail and see if you can find a general direction of travel.
Before you move into the area, and also while you are tracking, watch for magpies, crows, etc that may be above the area of the downed buck. (I bolded this because it has been a very successful method)
It's hard to tell by the color of blood where the hit was after it's been left overnight because any foam or frothy bubble that would indicate a lung pucture will have settled. Bright red could mean a good, lethal hit, but can also mean a leg hit. The lack of dark or other colored blood generally means no liver or gut hit but, right now, color means little. My guess is a leg hit and your larger area of blood is where he layed down.
You can also tell a bit from how high the blood is on surrounding vegitation.
Regardless of the location of the hit, it sounds like he is recoverable. Even a leg hit will make them want to lay down, especially with that amount of blood loss.
Don't assume the meat is ruined until you actually have the buck dressed and skinned. Because he hasn't been recovered yet, you have no way of knowing when he actually died so, much of the meat could still be good. Keep your eyes open in front of you because he could still be alive and you may jump him.
If you get to the point where the blood has stopped, you might have to start looking for other signs like tracks, but you can be fooled by the tracks of other deer in the area. If it gets to the point where you have to resort to following tracks or trails, watch for signatures like where a hoof has drug in the dirt that may allow you to differentiate your buck's track from others.
Wounded animals are less careful and also clumsier so, broken sticks and tumbled rocks are more common on their trails than those of healthy animals.
Good luck and thanks for being responsible in tracking him until you get him.