Farage is just positioning himself to be outside of any blame if Brexit fails, though. Regardless of my feelings about the Tories it would be hugely insulting to their voter base to not run a candidate in constituencies and instead ask people to support the Brexit Party.
Farage would pledge to give the Tories a clear run at all their existing seats and targets if the Brexit party were to get a similar deal in 80-90 constituencies. Johnson would also have to sign up unequivocally to a no-deal departure.
It seems like he’s offering an unacceptable deal to me. If the Brexit Party was just to agree to not run anyone then I guess that might work for the Tories.