How exactly does holy symbol work now (Post bb)

He's talking about 110% of the white base experience. The yellow party bonus experience is 10% of that 110%, or 11% of the monster's exp. White and yellow experience combined yields the 121% you are thinking of.

And he's fully aware of that, thus he mentioned the exp size being proportional to the party size.

I wrote something on Basil back in the day, let me pick it up. It's pretty simple though.

Yeah, they still have it.

And it's confirmed that HS' mechanism hasn't changed.