so since you have bread and coin I am not sure what steps you have done so I'll tell you everything.
1 take the bread and tell the guard it's hard, the guard with bite it and give it back.
2 use the bread one the suspicious looking stones on the walls of both the sides.
3 you might get a stick (I think from breaking a bar of the window) use that to dip in the pot with sticky liquid
4 use the stick to get what is in the vent.
5 you have to get a part of shard and use it on the pillow
6 you might have found a box from one of the stones and a piece of flint or coal (idk what it is) and feather from the pillow. Use that to light a fire and place it near the spider to get a coin.
7 combine coin and the box to get a lockpick and get out