If you have mostly crabgrass and the grass you had did not survive the pests, I think you need to just start over. Dig out the crabgrass you can. It could be worse, you could have California grass. Mow the crab grass to make sure it does not go to seed if you can't get to it all before then. There are organic weed killers. Boiling hot water will kill it. You need to set a big turkey cooker outside filled with water and take pot fulls of boiling water over to the weeds and douse them. It is time consuming but if you hoe up most of the smaller ones maybe there won't be so many left. Do this in sections and cover it immediately with cardboard or a weed barrier to keep weed seeds from invading the sections that are done.
I would look for a hardier grass for your area. Your grass will have a better chance to establish if you actually did some prep and added some compost and manure and till that in first. Before you plant keep the tiller handy. Water and remove any weeds that pop up and repeat until you don't see any more weeds coming up before you plant. Better yet, think about an artificial lawn or reducing the amount of lawn you have to what you can take care of.