oil filter backing plate

Marvel and a thin pry tool or a pick. Once you get an edge under just Zip around the diameter. As to the leak I'll bet the o-ring is pinched and not seated fully. Easy to do unless you can get eyes360 degrees on it.
Thanks, got it off using the screw driver thru the center hole, poped right off. Laid the plate on plate glass, only to discover it had a very slight warp to it. Ordered a
Canton Filter Plate with the eight holes already in it along with a "o" ring. Not too sure about an O ring vs single round gasket.