I had a rooster with frostbitten wattles and posted the same question a while ago. I read all the advice, decided he should be dubbed, but then I looked at the wattles and decided there was a lot of blood in there. I did not feel confident about doing dubbing myself, so I brought him to the local farm animal vet, who said:
1. It would bleed a lot, the tissue is highly vascularized.
2. It is not necessary.
3. The mild frostbite damage my rooster had was probably not painful to him, as he did not flinch while we handled the wattles.
4. You can tell if it is surface frostbite or deep by feeling the flesh to see if it is warm. If it is warm, there is still circulation and the flesh will live. The surface scabs will fall off eventually.
If your rooster had those symptoms he must have had a respiratory problems. Maybe he caught something, maybe it had something to do with the cold. If I had pneumonia I think getting something amputated might add a bit of stress to my life!