This was the first bootloader.bin that Spark uploaded to Github. I believe since then they have changed some stuff in it and added more watchdog timer stuff, and automatic recovery code that helps in the event that you get a bad OTA update. I’m pretty sure the bin I linked doesn’t have that stuff, it’s dated 1/26/2014 on my computer so you could correlate that with the github commits to find out what was in and what was not in the code.
The flashing slow looks good… you know, the Spark Core that I built I never got it to talk over USB, ever. DFU always failed. But everything in the USB circuitry was connected properly. Back then life was simpler though, just program the bootloader, update the cc3000 and flash your firmware. Now there are keys and ID’s and extra stuff, so you’d really probably want DFU mode. It would make life easier. I went back and tried to revive my old spark core v0.2 and for one, the hardware is just old. I didn’t have the buffer on the SPI bus, so it’s pretty much a museum piece now. Hopefully you started with V1.0 Spark Core schematic.