A note of caution. "... Using that as the basis for measurements of size of first anomoly and therefore distances on the reef shelf." ...assumes the shape is a particular size. Be very cautious when making that sort of assumption. We can't tell from the video what size anything is. The "landing gear" feature may be a foot tall, or 5 feet tall. The circular wire might be a 6-inch circlip (Richie suggested a retaining ring), or a tire bead (14 inch diameter?), or a barrel hoop (20 inch diameter), or a biological growth (how big is that?). Keep the unknowns in mind when studying the video, .
The obvious danger of assuming a particular size to any feature is in applying that assumption to other features, then use those features as proof of the size of the original feature. Until TIGHAR gets another ROV down there to examine the feature (assuming it can be found again), we won't know how big it is.
From the few stills I've seen, the cable and rope are the only features with anything like a known size, and even then it's hard to tell. What are their diameters? We can make assumptions, then apply thosee assumptions to other features that are in the field of view, but when the camera moves to some other part of the reef, the previous dimensions become assumptions again.
I love to read about people noticing things in the videos - getting lots of eyes to review what we already have can lead to important discoveries. Just remember the assumptions that support those discoveries. If and when any of those assumptions gets changed, then the whole argument based on the assumption will need to be revisited.