As for the data on the DC8 incident in 2000 being "Old", I note that the engines on it are CFM 56 - variants of which are fitted to aircraft today. More modern engines are only going to have higher T's and P's in the hot section as that determines thermodynamic efficiency.
I note that the DC8 had a "one off" experience with Ash. I also note that the Atlantic route is not flown "one off".
The report also gives the lie to the statement that there has never been damage associated with this event. As at 2000:
More than 100 commercial aircraft have unexpectedly encountered volcanic ash in flight and at airports in the past 20 years. Eight of these encounters caused varying degrees of in-flight loss of jet engine power (ref. 1). In some cases this nearly resulted in the crash of the airplane. Reference 5 explains that a range of damage may occur to aircraft that fly through an eruption cloud depending on the concentration of volcanic ash and gas aerosols in the cloud, the length of time the aircraft actually spends in the cloud, and the actions taken by the pilots to exit the cloud.
The engineers have said 2000 micrograms. That is the end of the story until the boffins have decided otherwise.
I would imagine that somewhere a test cell is being modified to allow ash ingestion to be studied in more detail.