Nikon has a few E type lenses (not to be confused with the totally different E-series lenses) with electromagnetic aperture diaphragms controlled from the camera electronically. An E type lens has a single letter "E" immediately following the maximum aperture of the lens in the lens' name. For example, AF-S Nikkor 105mm f/1.4E ED. Unfortunately almost all of them are either very expensive long telephoto, expensive wide aperture lenses, or very expensive Perspective Control lenses. PC lenses are also sometimes referred to as Tilt-Shift lenses. These E type lenses would allow more precise control of the aperture position by the camera than it is capable of with the mechanical linkage found in the overwhelming majority of Nikon F-mount lenses. But there will even be very miniscule variances in aperture size between frames with the E type lenses as the aperture is opened back up to the maximum between frames.

The problem you are encountering with your "G" type lens is that Nikon is still using a clunky mechanical lever left over from the 1950s to control the aperture in the vast majority of their lenses. Such a mechanical linkage is less precise and consistent than an electromagnetic servo motor attached directly to the aperture diaphragm and controlled electronically. That is the source of your inconsistency from shot to shot.

Your D3300 is not capable of using the technique used in the video referenced in your question. Even if you disconnect your lens and manage to set the aperture with a makeshift solution, the D3300 will not release the shutter, even in manual mode, when a lens is not detected.

Other camera manufacturers have changed over to electronic apertures as early as 1987 with the creation of the Canon EF lens for the new EOS line of cameras.

The aperture on such lenses can be "locked" in a single position by stopping down the lens to the desired aperture, holding down the Depth of Field Preview button (on EOS bodies that have a DoF Preview button or another button that can be remapped to that function), and disconnecting the lens from the electrical contacts between it and the camera body. Since the power contacts are the first to disconnect and the interface is designed so that the power contacts can't touch any of the other contacts on the lens this is perfectly safe and harms neither the camera, the lens, nor the photographer. Canon EOS cameras will also allow the shutter to be released in Manual exposure mode even when no lens is detected by the camera.