Battery Questions (Please help)

I want to start out by saying I've Googled, and searched forums, but if someone could give me a dumbed down answer, I'd appreciate it.

I have a 2015 Prius with 294,000 miles. Yesterday, I was an hour away from home, and "cooling performance of the hybrid battery is low" began to pop up. I drove the rest of the way (probably stupid). When I got home, I googled possible issues and it stated blocked air intake filter could be the cause. I cleaned it out and it was gross. I turned the car back on, and hooked in the OBD and that's when I got the triangle/ message to park my car in a safe place and check the hybrid system.

I considered trying to clean out the fan myself to see if that could be the problem, but after watching it, I think that's outside of my ability without my husband's assistance (he's traveling back and forth to be with his father who is in his end of life stage... so car repair is definitely not on his agenda).

Additional issues: decreased mpg within the last week (maybe 40 mpg) and when I started it this morning, the battery only showed 2 bars.

1. How would I differentiate a fan issue from a battery issue?

2. I really don't know where to take the car. I know the dealership is an option, but I'd just have to believe whatever they told me. Is there a way to find people who work on Hybrids other than the dealership? (Near Wilkes-Barre PA)

3. Is it worth replacing a battery if that's what is needed or should I buy a new car? My plan was to keep this car as long as possible due to financial reasons, but if keeping it will be more expensive in the long run... should I cut my losses?

Again, any answers you could give me in VERY basic language would be so appreciated right now. I know we've all had weeks where it's just bad news after bad news... and I think this is mine. So I truly appreciate your help.