To be fair, I predicted this too. Anyone who analyzed the trailers and videos they have been releasing could have predicted this.
For part 1: It became apparent after that chalk artist at Celebration VI put targeting reticules on about 9 or so characters, including Gallia, Ahsoka, and Rex with a caption saying "Who will survive?" or something to that effect. That alone made it predictable when combined with the fact we see the episode's duel in teasers for a while now.
For part 2: I have noticed Savage has had a new robot arm in almost every teaser video he has been in, which made it obvious. The same with Maul when his outfit changed and it appeared that he got his old legs back, implying his robot ones were destroyed/replaced.
For part 3: Yes since we have not seen any pirates in Maul's teasers and only seen Death Watch allying with him.
For part 4: This would be the iffy statement but considering part 2, it would be apparent at least both parties would be injured and retreating, if not the villains getting destroyed and be forced to run away.
Seeing Videos and Clips is different. Elliack was saying he/she could tell what was happening from the poor writing which I find it unbelievable.
And as for the person saying Savage is going to kill Galia? We knew she was going to die but how did you know it was Savage and Not Maul or any of the Mandalorians that would kill her?