In my experience, they take a while to recuperate. Make sure you don't overwater or underwater. Red leaves signal stress - what exactly, I can't tell. Soil looks dry & cracking. It looks very peaty...what soil did you use? They need good drainage. And like more moisture.

i repotted my chriatmas cactus six months ago and while it is fine, it hasn’t put on any new growth since since. They apparently do take a while to snap out of it. they don’t like to be dry

I don't understand why you would remove any of the roots. Your plant may not have enough roots left to support the growth above the soil line by drawing in water and nutrients. I hope your plant survives.

Patience. I went to repot my husband's 50+ year old Christmas cactus (his grandmother grew it on her roof deck in Brooklyn). To my surprise it was growing in water and pebbles all this time. The roots were dark and very brittle, so a lot damage happened in trying to pot it. For two years it struggled. Finally it is filling out. Two months ago it got flower buds and is now blooming better than ever.