Help me not to kill this phal (and avoid stem rot?)

[Pollicino]

Hi!
I'm back asking for help again.
I've always been afraid of mini phals, they seem so frail...
However, around Christmas, I bought this guy at Ikea. I couldn't resist!
Unfortunately, I'm a little concerned about its health. There's some blackness around the lower leaves and a few days ago it dropped the second-to-last and the third-to-last buds. At the same time, the roots seem happy to me.
So here are my questions:

• what kind of soil is this? Peat? Should I repot it ASAP? Now I prefer to repot my phals *after a while*, once I'm sure they are growing new roots. But this time I can't understand what's going on with this guy
• the black spot around the lower leaves, is it stem beginning to rot?
• the lower leaf showing mechanical damage, should I remove it once I repot the phal?

Thank you so much!