Responses
Spoiler ahead brrr
1. He became a slave because of the current nobles governing the place (the lady and her brother). We don't know what happened exactly yet. They say mc killed a noble when overcome with "madness" and that illness is what made him lose his memories and why he has to take medicine to this day. The medicine is what the lady and brother feed him so he doesn't recover his memories.
2. I think he was a general or a knight captain, but to mc he was His knight (a romantic promise?).
3. Not as of yet.

I marinated this too long I only remember about mc having an illness-- can anyone remind me + giving spoiler why did he become a slave and what's ML's position when mc was still a lord?
Why did that evil black haired guy become the lord?
I remembered that ML promised to take mc away but will it take a lot of chapters until we reach that part?