Thermostat housing bolt problems

What is your question?

I replaced my thermostat yesterday on my 3.0 1995 Mercury Sable. One of the top bolts was threaded fine, the other top bolt just was slipped all the way through with a nut on the backside to draw it tight. The bottom hole had no bolt and when I pulled housing off I saw that the bottom half of the female threaded hole was gone. The backside didn’t feel flat so I don’t think I can put a nut on the backside as someone else did on the top. I put it all back together with a little extra sealant at the bottom, but when I started it up 24 hours later coolant came dumping out at the bottom of housing. Anybody have a simple remedy for this?