Car will not start

My car wont turn over. I have a 1999 ford Taurus lx. The lights turn on and I think the battery is fine. My car over heated on the 30th of dec and stopped on the hwy when I was driving home, a 4 hour drive. I made it almost 4 hours. It turned over and drove a little further but it wouldnt go any faster than 40mpg and as it died the speed slowed to 30mpg til it just died. I let it sit overnight because it wouldnt start after it died a second time. I towed it to my apt. But it needs to be fixed and I dont know whats wrong.
Before I drove home, my dad replaced the thermostat because my heat wasnt working, and he said the radiator fluid was all gone, really empty. My mom said she didnt know how I got there with no fluid. When my boyfriend looked at my car after it died the second time, he said the fluid was gone to. He replaced it and I havent checked it since. What is wrong?

If its not?

How much would this be to repair?

Car was tinking, sort of metal on metal noise, and would not accelerate. All of a sudden the engine seized and would not start again, and began bellowing white smoke from above the alternator, from deeper in the engine bay. What could it be?

Does it matter if all the electrical is not working now? Does that change anything?

Would your diagnosis change if the electrical systems wont work? My lights and power lock, its like my car battery isnt working.

Have the batt checked along with the alt, hopefully thats all it is. Good luck hope I helped.

1999 Ford Taurus

My car started to over heat while on the high way and when my husband went to pull over and it stalled, he let it cooled down but the battery died so he tried to get a jump and it didnt work we replaced the battery and it still will not start. Someone told my husband vapor lock. What do you think?

Thank You! Will check it out.

I've had this car for just over a year. The last 6 months or so its gotten to where if I'm traveling for more than 30minutes it stars to xhocking out. I have to ether pull off and restart it or restart it in neutral. It doesn't get hot. And it only has to sit a minute or so before recranking. It gets up and goes just fine but if I'm going to travel for more than 30 miles. I'm on the side of the road. Help please!