2003 Mitsubishi Montero Overheating Issues

Hey all, here's the scenario. About a year ago, our '03 Montero (3.8L V6) overheated and the car stopped from a lack of coolant and from there it's all been downhill. We sorta put things off and only recently started to work on it. It's been having issues where the coolant system failed to work properly and we'd just refill it with coolant or distilled water and keep it running. After running for a bit, the radiator hoses would start to pressurize a lot (to the point where the hoses would bulge) so we started to drive it less and less often to prevent destroying it more than necessary.Earlier today we were getting ready to go camping and were meeting at a friend's house about half an hour away to set out. The drive was main road, highway, city to get an idea of how fast we were going and how often we were stopping. It was about 110 degrees outside so we were already concerned and drove in the slow lane with 65 MPH to not push the car. Just before we got on the highway, the oil light (red one) came on for a couple seconds at a red light then turned off. Everything was fine on the highway and once we got off the red light came on again but didn't go away. For the last portion of the drive we were testing it and found it only comes on when the engine is below 800 RPM, even while moving (in neutral since it's an auto). Once we got to our friend's house we noticed the temperature gauge was almost maxed. We immediately shut off the car and poured water on the radiator to cool it off and let the system depressurize. Ended up coming home and had to stop twice to let the engine cool off since there was traffic. We left the heater on at full blast to help cool the engine but in the grand scheme of things, it only delayed the overheating. The oil light still comes on once the car is warm and basically idling.We have plenty of evidence from previous tests to believe the head gaskets are shot and are going to replace them (car's being disassembled as I type this) but what else could be wrong? The oil light has never come on before and the temperature gauge was higher than ever before. Granted, we've never drove the car in this extreme temperature since the whole issue stared but it seems that all these symptoms should be caused by something else. Long story short, can this car be fixed or is it a lost battle already.EDIT: Forgot to add, a few weeks ago, we tried to use this Irontite repair product in an attempt to fix the system but there was an issue. The second step (the ceramic seal) was supposed to stay in the car for 24 hours then the ENTIRE coolant system had to be drained, not flushed. The model Montero we have doesn't have coolant drain bolts on the engine block like it should so the ceramic was in the engine for about 3 days before we ended up just trying to flush it out. Not sure if this can be a game changer but figured it's an important part. Thanks everyone. via /r/cars http://ift.tt/2rWIVOi