A Humanoid male with the power to manipulate ice with a split personality
Before I start, let me say that this is not encouraging. If this is the best description of your article, you don't have a very good article. I wrote 2241 which I could describe as a superhero who the Foundation likes and even call him by his real name… but it would be more accurate to the story to say that he's a child who the Foundation experiments on to learn how anomalous powers develop and who they will murder the second things get out of hand - if they can manage it.
SCP-XXXX is to be kept locked up in a 5 m x 5 m x 5 m room
Nope. Unless being in a room of that exact shape and size somehow stops him from doing anomalous stuff, don't do that. Put him in a humanoid containment chamber.
Subject does not seem to be hindered by harsh temperatures or requires food or drink to survive.
This doesn't belong in the containment procedures. Also, if he's not hindered by harsh temperatures, the heaters are pointless. "Harsh" doesn't mean "cold."
SCP-XXXX is a Humanoid male of average build measuring 1.8 meters in height with pure white hair measuring 15.7 cm and wearing an unusual attire including one velvet indigo colored cloak, one black waistcoat, one pair of black dress pants, two gauntlets with vambrace on each arm and two greaves on each leg
Nope. Firstly, it's "humanoid."
Secondly, unless his hair is anomalous only the colour really matters.
Thirdly, he's gonna wear what the foundation gives him unless the clothes are also anomalous.
Fourthly, you describe him like a book character. The Foundation isn't writing a book. They're reporting on a dangerous anomaly they are keeping prisoner.
freezing them instantaneously and weaponize them to a considerable degree.
Tense agreement problems - it'd be "weaponizing them" not "weaponize them"
within a 30' radius
Imperial measurements are bad, don't use them.
Overall, the worries I expressed at the start are confirmed. I will say that you were right to say "dissociative identity disorder" rather than "schizophrenia" and in that you avoided a common mistake.
That said, there's a more interesting story to tell than you do here. As I understand it - although I may be wrong - DID is often caused by trauma and can be co-morbid with C-PTSD. Therefore something happened to this guy. That's more interesting than "he has ice powers and is sometimes scary and sometimes not." Hell, maybe that's how he got ice powers.
If you're set on continuing this idea, I'd advise researching DID, maybe talk to sufferers, that short of thing. If you're not going to research it and talk to sufferers, cut the multiple personality stuff entirely.
Also, read more humanoids on the site. See how they were successful and why. Check out the comments section of those articles too, see what people don't like and why.