I did not find a fix. In the end I ended up uninstalling and removing the entire USPS module. It is so buggy it is unusable.
I manually added First Class to the Carriers list and typed in the weight breaks and prices by zone by hand based on the spreadsheet from USPS website for Commercial Base pricing, and I added the rest of the USPS methods and rates through SQL from spreadsheets as well.
A lot of setup work, but it is working great now. For rates, go here: https://www.usps.com/business/prices.htm, click on Downloadable Files, scroll down to First-Class Package Service®, and download the XLS corresponding to your rate class (Commercial Base or Commercial Plus). There are only 13 oz possible, so you only have to set up max 13 ranges. Since you are doing this manually, don't forget to subtract your package weight from 13, and shift the entire rates table up (so for example I use the 13 oz price for 0.75-0.8125 lbs. range to account for a 3 oz package weight).
This is doable for First Class, Media Mail, and Library Mail, since these services are not zone-based. Zone-based services (Priority Mail, UPS, Fedex, etc) are more difficult, and probably required SQL.