Thanks everyone for the response!
Some UPDATE:
He talked today to the mechanic that installed the gears in January 2021. He also changed the diff fluid about 1.5-2 months ago max. So, I guess he inspected the gears at that time too.
He claimed again that he need to change to Dana 44 axle with 4.88 gears, otherwise Dana 35's 4.88 are going to break again.
He also told him that by installing a locker, it might help, since the gears are going to "suffer" less.
What do you think about his statements?