If adb sideload isn't working, it is usually a driver problem or you failed to start adb sideload on the device... Try using some of the driver installation tools and tips from Wugfresh's toolkit, using the "stock" adb drivers can be problematic for some people in fastboot.
As long as fastboot is working, just flash TWRP and sideload from there (sometimes it works better than the stock sideload), if that fails, return to stock and don't wipe internal storage until AFTER you flash the ROM this time.
Current Personal Phone: Google Nexus 4 on Cricket/Aio (Beanstalk
4.4.4 with hells-Core Kernel
Current Work Phone: LG G2 VS980 on VZW (AICP
Current Tablet: iPad 4 and Samsung Galaxy Note Pro 12.2
Other phones "in the family": HTC DNA, HTC One (M7), Motorola Moto G GPE
Previous/Retired Android Devices: HTC Aria, HTC Incredible 2, HTC Rezound, Samsung Stratosphere, Samsung Galaxy S2 Skyrocket, Nextbook 8P