How likely is it for fat necrosis / adipose tissue damage to heal with time? and if so, how long does this usually take? (affected area thigh). thank you in advance :?

It is going to heal however the timing depends greatly on the immunity of individuals. If the inflammation is not too much nor having symptoms that inflammation is beyond the local area of involvement, I would suggest to be optimistic and love yourself, because that in itself speeds healing and limits scarring. The more inflammation the longer it takes to heal and the more the scar.