My opinion, for what it is worth (only have done three MLF secondary ferments).
If there was a noticeable taste change, you definitely got the MLF going. Other than throwing in a whole bunch of SO2 or dropping the temperature 20 degrees, I doubt there is anything you could do to interrupt it. My guess after eight weeks is that it is done.
Are you sure you can't get more test strips or a test kit to verify this? Would be the safest thing to do. If not, the only downfall I know of, is that the ferment could start up again in the bottle. I highly doubt this could happen, as I highly doubt you could arrest a MLF fermentation once it gets going.
Just my 1.5 cents (inflation) worth.