Firstly, The Omni Kings marking off fighters on the Godpad is only a formality and doesn't really have to do with a fighter being completely eliminated. The reason I make this argument is because of Episode 110. After the Spirit Bomb clash between Goku and Jiren, Goku was presumed to be dead and there was a scene where the Omni Kings were right about to push the button, the world of void began to shake because of Goku. If Goku was a few seconds late, the Omni Kings would've pushed the button and would have to redo the same if Goku hadn't actually died because it was an error on their parts and not the contestant's part.
We also know by this that a contestant doesn't necessarily have to only be knocked out to get eliminated. If he or she is either disqualified for violating a rule or dies or is in any position where the fighter cannot continue to fight in the tournament of power, the fighter is considered to be eliminated.
So to answer your main question. Yes! Android 17 was presumed to be dead just like Goku was which as a result, meant elimination.
As for the other questions, The Omni Kings and even The Grand Priest were under the impression that Android 17 did die during the self-destruction. We know this based on what he said right after, where Jiren wasn't going to be disqualified because Android 17 chose to kill himself. Even in Episode 110, the Grand Priest initially assumed that Goku died after the Spirit Bomb Struggle as he clearly stated that Jiren wouldn't be disqualified as Goku died as a result of his own attack. With regard to them not showing the official elimination of Android 17(ie Marking him out on the God Pad), is something only the staff and writers would know. Perhaps there wasn't sufficient time in the episode to include this bit of animation or maybe because Android 17's death was confirmed by multiple characters(Based on Goku's, Vegeta's, Universe 7 fighters, Jiren's, Grand Priest's etc comments) and there wasn't really a reason to indicate the same or perhaps they left this out because of what which happens in episode 130.
Based on my Initial Argument, I personally believe it honestly d wouldn't make a difference if they were to have marked Android 17 out. It would've just been considered an error in judgment which they would have redone. It would only matter if pressing the button on the Godpad causes the character to get erased or creates some form of restriction that prevents them from fighting in the tournament of power. As of now, it is solely there for the entertainment purposes and as a list for the Omni Kings to keep track of the fighters remaining.