Regarding your DC problem, that sounds familiar - have you seen these threads:
Regarding the latency, everything I did to reduce the latency is described above in this thread. The three things that fixed the latency issue for me were changing config.PerformanceLatency parameter, switching to using the SoapyUHD GNU Radio block rather than grOsmoSDR block, and increasing the sampling rate as high as I could (before I started getting segmentation faults).
