With regard to your question about poor performance on your homebrew LFA-
My understanding is that resonance is greatly affected in long boom Yagi-Uda arrays by the boom type. It is not simply a matter of changing the dimensions of the DE but also the parasitic element lengths and spacing. The ARRL Antenna book 23rd edition has a detailed section on the new LFA and OFA antennas, and they caution readers to stick to the 'cookbook' closely or expect to spend a lot of time modeling the new configuration. On short booms, the differences don't make so much difference, but when the boom gets to be several wavelengths long it is an increasingly important factor in radiation pattern and resonance of the parasitic elements.
The difference in width of your loop and the DE width is likely also an issue.
Have you done any computer modeling of your design?