Hi Lindy,
First welcome to the forum.
Take my comments with a grain of salt, as I am no vocal coach or expert.
I love the song Man in the mirror. I am a huge fan of Michael Jackson RIP. No, you didnt butcher the song at all. Yes, there were parts you were flat, but what I noticed mostly is that the renditions tempo was too fast. In my opinion it removes the feel... I recommend to slow it down a bit.
I think you have a nice tone to your voice, and you play nicely along. Superb!
Best of luck, and I would love to hear it again slower
Wondering to hear what the others will say.
Gilad