To answer your second question...it's a bit complicated so I'll try to make sure I explain it accurately.
"A bell clanged against her heart" symbolizes the feelings she used to feel in regards to her father's violence. Brieftly, in the beginning, Joyce makes reference to her fathers violence and her thinking that is what causes her heart palpitations. I don't know if you know what palpitations are, but basically your heart is racing, it feels like it's going to thud right out of your chest. It's quick and somewhat frightening. Eveline is thinking about all that she is going to leave behind and all that it waiting for her and she is unsure if she should get on the boat.
When the whistle blows her heart reacts because that is how palpitations work. A startling sound can cause them, just like a sharp fear can cause them. Immediately she associated the boat with "danger" because her heart reacted. It only reacted to her father's violence, and now it is reacting to her situation.
Just after the statement "a bell clanged against her heart" she became worried and scared...even stating, "All the seas of the world tumbled about her heart. He was drawing her into them: he would drown her."
It symbolizes her fear and maybe even distrust of her safety in her situation.
Maybe she thinks if she got on the boat things wouldn't be different. She grew up with the fear against her father, and thought she was escaping it, only to think that she might truly end up like her mother, which she said she did not want to--I think this refers to the type of marriage her mother was in as it is clear her father was abusive to both her and her mother.
I hope this helps.