Unless the TFTP is not working at all, here is my suggestion for you:
I wrote a resume for two procedures reported as working from two different users; may I suggest that you follow the "using sysupgrade", the first step only?
What I propose is to use the TFTP method again (with instructions provided) but using this firmware instead, a stripped one. Usually things work better when the U-Boot partition is removed from the firmware binary for TFTP.
This should get you back to stock firmware if everything works fine.