I wouldn't use threadlock. That's what the lock nut is for.
I think you mean you damaged the flats on the outside of the nut, so the impact wrench socket no longer grips it? If so, this time I suggest you take it to a mechanic or the dealer, for them to remove the two nuts, they can also use a die to strip the threadlock off the spindle bolt, i suggest you get them to do this, to avoid damaging the threads in future and they can replace the 2 nuts. Chalk it up to experience and start afresh next time.
I wouldn't soldier on with your impact wrench, if I were you. Call me old fashioned, but I don't own an impact wrench. If I did, I think I would avoid using it on an Enfield. Too sudden and powerful, not enough 'feel'. Happy to be corrected.