1) it depends on what day you go as to when it opens. I believe that on saturdays it doesn't open until 10 or 11 to let the bikers enjoy it, but i think every other day it opens at 8
2) You should be able to see the trail when you enter and exit the horseshoe
3) see above
4) the trail follows the river the whole length pretty much except for the horseshoes.
From my understanding, it takes all day of really hustling fishing the big horseshoe. Due to the fact that the days length isn't at their peak just yet, i would think of maybe just hiking part of the horseshoe to make sure you are able to get back in time. If you have a gps, that would be good also that way you will know how much farther you have to go. Just be careful about the time, i believe i've heard that every year there is at least one fisherman who spends an unwanted night back in there. If you go, let us know how you do though.