You are doing well, salt dips are not always for the faint hearted, specially when you see them roll. Keep up the water changes the temp rise was also a good move. You might see the slime coat drop off the fish after a salt dip but this is a normal reaction.

The spot on the tail could be a point of infection or ulcer. You could salt dip or I would carefully remove him and topically apply some Maracyn or Furan 2 directly to the ulcer with a cotton bud. You can do this daily but should start to heal within a week ime