Can ADS-B DF-17 messages with a non-zero remainder after CRC check be used?
Messages with Downlink Format 17 are, as you know, ADS-B messages that do not require interrogation. As such the interrogator ID will be zero. 

Frequently you will see that, after applying the CRC check, the CRC remainder is non-zero. This is caused by corruption of the ADS-B message between the transmitter (see note) and the receiver. This is partly because transmissions of multiple aircraft are unsynchronised so that they may overlap an become difficult to untangle. This overlapping is called garbling. 

Since you have IQ information available, you may be able to de-garble overlapping message with some success. Also, you could try to do error correction using the CRC algorithm. Up to two rogue bits can usually be corrected, more than that becomes difficult. 

To improve the performance of the CRC error correction you can again use information from the IQ sampling, by giving each bit a confidence value based on the shape of the received radio data.

If you are not able to correct the error bits (i.e. you have a non-zero remainder after correction), you should consider that ADS-B message as useless. 



Note: there are a couple of aircraft flying with rogue transponders that transmit garbage DF-17 messages with non-zero remainder. They will be phased out in the next couple of years.