I think you should keep two things in mind in trying to break 8 hours and something not to worry about.

First, don't waste time. Go into aid stations with a plan. Have the top of your bottle off when you get in to the aid station, drink some cups while they're filling your bottle, and then be out of there as they give you the bottle back. Gotta pee? Hold it for a while. You could save a minute or two by reducing the number of potty stops. Trust me, these will be tempting during the non-stop run of the tow path.

Second, commit yourself to running pretty much all of the tow path and all of the road, except its very steepest of hills. Don't go out hard on the first climb to the AT and don't work too hard on the trail. You need to have your legs under you when you hit the tow path. Keep the effort under control when you do hit the tow path. An easy pace at mile 18 will be a huge ass effort at mile 41… if you can even do it!

Don't be too worried about the splits. I didn't at all. Go out controlled, get into a steady easy rhythm on the tow path, stay tough the latter half of the tow path, and then dig deep those last 8 miles!