What does this combination of symptoms & error codes mean?

I have a 2001 Prizm with a bunch of error codes, and while each code has a multitude of possible causes, I'm wondering if the combination of codes can help narrow it down, along with the symptoms.

There's actually only one symptom: a precipitous drop in gas mileage. Typically over 300 miles before the fuel warning light comes up, but the last couple of tanks this has dropped to about 200. Otherwise the car seems to drive fine.

I hooked up a basic OBD tester I have and came up with the following codes:

P0125
P0171
P1349

And the following "pending codes"

P0130
P0133
P0171

From looking around it seems to me like 0125 relates to a possible thermostat issue, 0130 and 0133 indicate an oxygen sensor or the like, 0171 to a possible MAF sensor or something related, and 1349 indicates a VVT issue. But I'm aware that many of these things are inter-related.

The coolant level is full, the engine oil level is fine, the air filter is OK. I took out the MAF sensor and soaked it in isopropyl alcohol (the local stores are out of MAF cleaner) let it dry and reinstalled it this morning. (My wife drove it since then and said it might be driving a bit smoother but she wasn't sure. It seemed to me like the soaking cleaned it somewhat, but I don't know what a clean MAF sensor is supposed to look like, so not really sure.)

Anyway, my question is: based on the combination of codes and symptoms, can someone make an educated guess as to what is the underlying issue?

Thanks.