If you do want to sell, there’s people looking for an FP1 here - however I would urge you to be fair and honest about the potentially broken USB connector. Alternatively, offer it for parts so someone can fix their phone.
Otherwise, fairphone have a recycling programme to which you can send your phone for free here.
About the battery performance - have you checked whether the battery may be failing? If it started to swell (and therefore spins on a flat surface, see here) you can get it replaced on warranty. My battery lasts about 3 days with what I call modest use, but our definitions of modest may differ.