Veterans, please help me! Red triangle, error codes P3018 P0A80 no turbulence in inverter coolant

Please excuse typos, I wrote this on my phone. The main red triangle warning light came on along with the (!), VSC, CHECK ENGINE. My car has been getting poor gas mileage 35-38mpg for the last month or two before this. I also noticed it was low on oil last time I changed the oil about 2.5 quarts. It is a 2006 standard Prius with 195,000 miles. I googled the codes and they say, the P3018 is battery pack 8 becomes weak. P0A80 Battery over temperature, replace hybrid battery pack. I investigated this and found out that the inverter coolant pump may be an issue. In power-on mode the pump makes the aquarium pump noise but when I took off the reservoir cap there was no visible turbulence, the liquid was still. I felt the pump and it vibrates & hums slightly, but the coolant doesn't move. When I am driving the battery goes from green to two purple bars pretty regularly, which didn't happen before the light came on. After the lights came on the battery cooling fan ran constantly, then I took the carpet and rear tire plastic holder thing out of the back because a mechanic told me that those warning lights come on when there is water on the hybrid battery. I found no water, but put a big floor fan in the back and blew it on the battery over night to make sure it was dry. The next morning the battery cooling fan didn't come on, but the warning lights were still there and now my car revs higher than it was, like the transmission is stuck in a lower gear and then smoothed out. The acceleration is also poor, but I never thought it was that peppy but it is noticbly worse now. I want to fix this, but I really don't know what to buy first. I am thinking about getting a new inverter coolant pump, but the one I have in there does have the silver bracket, which I thought meant was the new one that didn't suck. I also was thinking about getting a salvaged battery cooling fan since mine doesn't constant run like I think it should with the error codes I have and I think I may have broke it by blowing that fan on the battery pack all night. I also was going to check the inverter because I drove the car a bit -30 miles, before knowing that if the inverter coolant pump shows no turbulence I could be burning up my inverter. And of course I am thinking I need to replace the hybrid battery pack with probably a Dorman because the only game in town where I live, central Illinois, is the dealership and they said just the battery replacement would be 5-6k. My car is valuable for transportation, but I would like to keep this repair to at or under 2000 for me to feel like I am not throwing money away. I welcome your suggestions. Thanks so much in advance and have a great day!