I feel like Ianto, if he had angst, would keep it to himself -- but I also think that he'd be reasonably confident for at least a year that Jack would find them and get them home, so he probably wouldn't angst, he'd just get on with things until Jack found them. :D

Jack is probably flailing, on the other end, but that's not as interesting as Gwen and Ianto settling into the early 19th century and entertaining themselves...