The 6 ft offset is OK and is better than 3 ft offset. To understand the issues, think of the radiation portion of the antenna projecting visible light. The further the radiating dipoles are from the tower, the less the tower blocks signal in that direction. The tower is made up of vertical pipes and diagonal steel. There may also be vertical transmission lines and other antennas mounted on the tower, at the same elevation as your antenna. All of these elements WILL either block the signal through the tower or cause reflections, like multi-path, in the general direction of the tower, from your antenna dipoles. From your diagram, that would appear to be NNW from the tower site. I hope there is no critical coverage required in that direction.
The way the antenna is orientated, your best coverage will be South, then East and West -3 dB down, then NE -6 dB down and last NW more than -6 dB down, due to the tower steel, braces, transmission lines and any antennas blocking the signal. Keep in mind, you are operating at VHF, so any open space on the tower adjacent to your antenna, that is smaller than a quarter wavelength [approx 18"] will not pass signal. Visualize the 36 inch tower face with vertical runs of coax and waveguide say 15 inches or less apart. VHF signals will not pass through there and will appear as a solid surface to your radio waves, blocking your signal. That is why an open grid microwave works. see image below.
In addition, in the areas of NE and NW, you will also suffer somewhat from multi-path caused by tower reflections.
Please do not consider this evaluation as terrible. This is the real world and this will probably work very well, except in the NNW direction. The only way to achieve perfect omni coverage from side mounting on a tower is to use two, 3 or 4 directional antennas mounted around the tower. Like you would do on the sides of Empire State Building, for example. I hope this helps in your understanding.
