Vale Wildlife hospital have done research into how well amputees survive in the wild and they are saying they do well. BHPS guidance is along the same lines.
However, the amputation must be full leg so no stump is left and it goes without saying it must be rear leg and not front ( these should be put to sleep as they cannot dig for food )
I had one amputee hog that lasted several years without any issues in an enclosed garden with another hog
Ticks once they’ve gorged themselves drop off normally, therefore as long as the hog is healthy it should cope alright with an amputation. However, a sick hog can have issues with parasites regardless of how many legs it’s got.
In closing though I really think it’s up to the vet/carer to make this decision for the hog and this needs to be based on general state/age of hog, finance ( sorry but the cost of amputation could save several hogs ), area they are going back to – are there a lot of people feeding in that area, and also gut instinct.
I don’t think there is a right or wrong until we get considerable more research.