And even if we ignore the realitities of life referred to by OS and MFS the theory also states that stalling speed is proportional to the square root of the weight. So doubling the weight will multiply the stalling speed by a factor or 1.41.
If we assume that VR is affected by weight to the same degree, we can multiply your original VR figure of 110 by 1.41 we get 155.1. This is less than the quoted VR value of 110 + 67 = 177 at 400 000.
This makes your "only an extra 67 knots to produce double the lift" appear to be excessive, rather than surprising small.