2003 Chevy Astro Engine starting problems

A couple of weeks ago, we had sub zero temps here. When trying to start the van one morning the battery was dead. I ran jumper cables to my truck and the engine cranked right over but refused to start. I took a guess that I may have a frozen fuel line. I put a couple heaters under the van for a day and was able to get the engine to start. BUT. The engine does not start right. The engine acts if it is slowly building up speed until it is running. It only runs if you keep your foot on the gas. There is black soot all over the snow by the tail pipe. What could be causing all these things to happen?