Shannon - I will gladly be a prayer warrior for you and your family. You have been such a beacon of light on this board with your Christlike demeanor. I will be praying, and the Lord is an excellent listener. He knows your every need and will provide. He is a God of love and compassion, and He will be by your side through this time.
I am thinking that it would be a very good time for a new start with LHFHG, but I agree starting half-speed would be good. I think you'll be able to tell then if it is a good idea to go full-speed, half-speed, or take a break. I also think it may be a good time to set up some type of structure to the day, as you have identified that was a good thing, and it is something you feel you are missing now.
LHFHG half-speed each day will provide some routine, but I wonder if it would be a good idea to add to that by choosing something special each day for the 2 of you to just enjoy? For example, Mondays could be pizza and a movie day. I have found when my dh is gone I like to do this with my dc. We have seen some excellent movies together - "Facing the Giants", "National Treasure", "October Sky", "Iron Will", "Tangled" to name a few. We have to look hard for kid-safe movies, and there are a few things to discuss along the way, but this is something we have learned to love to do.

Maybe Tuesdays could be cooking days? My dc love to cook with me, and I bet your sis' would love to be surprised by this. You could make it super simple or go all out - but the fun could be in choosing what to make from recipe books and shopping for things for the meal together. You could have a theme too - like Mexican food, Italian food, etc. Wednesdays could be outdoors days - maybe you could ride bikes through the park together and have a picnic lunch? Thursdays could be an encourage others day. Maybe you could write cards to someone, or bring someone a treat or give someone a call. Fridays could be eat lunch out at a different restaurant each time? Or hot cocoa at Barnes and Noble with some reading time? Or an outing to the zoo? I'm not sure if any of this would work, but I have been trying to do some things like this and have enjoyed it. I find I often feel tired and over-stretched like I can't do these things, but then find once I am doing them, I feel more refreshed and happier. I hope something here can help, but if not, just totally disregard this. I will be praying for you.
Love in Christ,
Julie