I have taken an empty bottle through security in carry-on before now, I don't know whether they'd get annoyed if they found it, given that it's no worse than buying a full one in the departure lounge and tipping out the contents.
You can transfer your scotch when you recover your bags, although it's a case of whether you trust the subsequent handling of your bag to keep the bottle intact.
As for bus station to T4, you might have to descend to the railway - I think the HEX is free between terminals but check that.