If Jack didn't already have his suspicions, he would now. The way the selkie refuses to face him does so little to engender trust in the pirate. He narrows his eyes as if it will enable him to see into the selkie --see through him-- and know the truth.
The warnings are considered, though very briefly. If Jack were to keep friends or family for long, perhaps it would matter more. His only true love will last as long as he's there to mend and care for her. The bit about still feeling pain and being wounded but living on makes him cringe a bit, but he just meets the rest with a bored nod.
"Yeah. I think I can square with that. ... Turn around and look at me, would you?"