That length is almost 3 wavelengths at 20m, and should definitely show
gain.
It is essentially the first half of the rhombic from the Antenna book.

How high is the vee compared to the yagi? Are the wires uniformly high
or do they slope?
Vee is at 35 feet at the feed, and 25 ft at the ends (corners when it is a
rhombic).
Yagi is at 40 ft.

What is the angle between the two legs?
52 degrees, equivalent to a 64 degree tilt angle when it is a rhombic
(maybe tomorrow),

Are you feeding it with open wire line? If so, that could be picking up
noise depending on where you route it and your local noise sources.
Yes.