Would there be water in the oil/oil pan if the water pump was bad?

have car cooling system pressure tested to determine leak source. could be therm housing issue or water pump under timg cover

Have you checked the carpet inside passenger side for wetness? Could be leaking at heater core but, Sounds like the thermostat housing was part of the issue. Don't tighten the bolts to tight on the housing it is made of plastic and could break or warp causing it to leak again. I agree with you at this point about the water pump not being the issue because it is mounted internally and would leak water into the oil pan. You need to do a cooling system pressure check and look for external leaks with that. You can also add dye to the cooling system so that the leak will show up easier. If you don't find anything this way do a compression test and look for leak at head gaskets or intake.