Ok spoke to Ray Hall, extremely helpful as usual. Emailed him the map and he was on the phone 10 mins later, confirmed the dwell is fine, if anything a touch on the conservative side.
Asked about the V88 and he said it would allow more dwell but he doesn't believe the V44 is the cause in any case so nothing to be gained by switching to V88 his view.
He suggested it's most likely either a voltage spike, in which case the ecu would probably have been fried, or a poor earth, and to call Mark at Godzilla motorsport. Again, Mark was really helpful. He also suggested a poor earth.