You're right. if we count considering that Isildur need to be alive at the end of the Second Age and I think they can't deviate from that, everything must be happening within a (Numenorean) lifetime of 3441 SA. The time condensing also seem to occur, with Isildur, which was suppoed to be an adult by the time of Tar-Palantir's death while he seems to be still a young adult in the show.
Anyhow, the 3255 timemark seems right to be the coincidence of calendars between Tolkien and Amazon's Second Ages. That makes Galadriel around 5,500 years old. Sure, she'll age 3,000 more years into the Third Age, maybe changing her character (though I don't buy it as she is already wise in the Second Age) but... it makes very difficult for the writers to implement significant character change over the very short time of the series. If we're to follow Theo to the end of season 5 (I have this hunch), it will be a very short time to mature for Galadriel between millenial stasis of her character.