what would cause my van to rough start almost backfire steam and exes of water comming out of the exaust and litght the service engine on and it wount stop, it runs like if its running out of gas, pings and knocks. i'd apretiate a little help.

The other day, while driving, my van went into serious overheat mode. We had just checked the fluids and they were fine. I checked the antifreeze reservoir, it was completely empty so I filled with what I had left in the jug. The heat gauge went down and all seemed to be ok. The reservoir needed filling a couple of times, but I thought that if it had actually leaked out, that would be normal. 2 days after, when I started driving, the motor started squealing like mad, van could barely be accelerated, seemed like very little power. We decided it was the water pump and changed that. That reduced the squealing but didn't stop it. The van did run better. However, during the trip, I ended up with no interior heat at all and the van did start to overheat slightly. I thought that maybe we hadn't filled the rad enough and planned to fill when I got back home. After driving for about 45 minutes, I started to get some heat but then seen vapour pouring out of the engine compartment and really overheating again. A lot of engine knocking/rattling also - before and after water pump change. Checked the oil, it wasn't really milky but there was a tiny, tiny bit of white residue on the dip stick. The dipstick indicated overflowing oil... wayyy up on the dipstick but the crankcase seems empty. Are these all related issues or do I have a ton of problems on my hands? Thanks in advance for any and all help.