Hello,
"So the other day when I was playing Minecraft someone went to tier test me." ... and "as always" have promised you a free rank.. cape..?
You should learn the lesson that if somebody is offering to give you something for free, then that's 99% a scam.
The hacker, by this time, probably has already done everything to keep your account from being recovered. You still may have some chances with this form https://account.live.com/acsr, but nothing else can be recommended.
But there's a catch: if the hacker has added 2FA to your account, "This form won't help if you have two-step verification, because no one, including our support team, can access your account without additional security information.", so almost with 99% chance I can say you won't get your account back.
Regarding your username, try checking back periodically to see if the username becomes available. I'd say every three months. There's a chance the hacker will change it, and after the 37-day cooldown, the username will become available.
Good luck with the YouTube stuff. Just as a tip, you could make a video about your case so more people would know about this common scam.
Upd: I have just found out you might have luck with getting support from Minecraft support:
But they would 100% need your Transaction ID:
https://help.minecraft.net/hc/en-us/articles/360029977371-What-is-a-Transaction-ID
Also, I suggest you taking a look at this video about this scam:
https://www.youtube.com/watch?v=QXHGFXq28oQ (especially 4:30 timecode)
I have very big doubts that Minecraft support can recover your Microsoft account, but at least they might help you with your username concern. I wouldn't count on that, but as you're "willing to do whatever it takes", then this is the thing you can try