if I lost an engine the autothrust for example, and therefore CAT2 showing on the FMA, can I autoland?
After an engine failure and no other non-related additional failure, you'll still get cat 3 single on the FMA!!! (ref FCOM 3.02.70 p15)
But a cat 2 indication on the FMA is all you need to be allowed to perform an autoland after an app to cat 2 minima.