1999 Ford Taurus will not start

My husband drives this car to work and has for a while with no problems. It is a 1999 Ford Taurus, 135,000 miles, V6 3.0 DOHC. Problem started a couple months ago. It broke down on the way to work and we had to replace the power-steering pump & belt. On the next day he drove it, he said the check engine started flashing, speedometer went crazy, & it didn't seem to be shifting correctly. He parked, worked 12 hours and came back to a dead car. It wouldn't turn over. No power at all. We replaced the battery & speed sensor. It started up but when you turned it off the battery light remains lit & theft light flashes. If you don't unhook negative battery cable it won't restart later. We drove like this one trip then just had to replace water pump. After trying it out, noticed when it wouldn't start, you could rake negative cable connector to it's post, causing wipers to come on and it would then start. Now I am back to no start at all, but flashing lights, door chime, and other electrical equipment is working. Please help. Ready to send to junkyard. Thanks, all help appreciated!