As someone who's attempting to make an entire MU chart for the game, it's impossible to complete one without having proper knowledge on all of the characters. The best way to go about this is to seek out individuals who excel in their characters' skillset and take notes from your matches with them in addition to labbing specific aspets of each match up. Don't get me wrong, I thoroughly appreciate the effort that was put into this. The time put in for the labbing and the written explanations are great, and I really think we need more people in the community who are willing to put in labbing for data for tier lists, MU charts, etc.
All of that being said. I believe there is a bit of lack of information here that yes, while being your own chart and opinion (and there's absolutely nothing wrong with that), reflects a very misleading match up chart from simply not being very knowledgable in a large handful of characters. A large contributor to this is not using live players for your testing and instead relying on CPUs and Vanilla Brawl's ai. It's heavily worth mentioning that (at least for most characters iirc) Minus still uses Vanilla Brawl's ai despite Minus's moves changes. This creates issues like CPU Bowser using grounded Royal Rampage to edge guard because he thinks it's Fire Breathe.
So anyway, to make an example of this, two things I would like to address specifically are your placements of Sheik and Ice Climbers.
A good player to discuss Sheik with would be Young Boy Bread. I'm personally very unfamiliar with anything techical to do with the character, but from playing his Sheik and seeing the potential of Sheik's combo, punish, and neutral options, I feel like you've neglected a lot of what Sheik can do against Bowser or are possibly praising Bowser's armor just a little too much.
For Ice Climbers, I would agree with your placement, but there's a problem with your statements made, and it ties into my main point of not being very familiar with characters when making a MU chart. Ice Climbers can kill most characters at roughly 150% from a Popo grab>dthrow>Nana fsmash so the "not dying at 270%" shouldn't be a thing. They have an "infinite" jab lock on Bowser (Popo grab>dthrow>Nana SH fair sweetspot meteor> dysinc ice block from both climbers) that can get a pretty free amount of damage as long as Bowser misses the tech. In general it's worth mentioning that Bowser is the best character to do jab locking on because of the nature of Bowser and I didn't see note of this anywhere.
My point is that for a more accurate MU chart, you would be a lot better off investing your time in playing real people for much more accurate data.