Hi there
My 7yo dd takes about an hour, hour and a half to eat her tea most nights. And it's not difficult food to eat.
She has a very narrow range of food that she'll eat, but most of it's pure, unadulterated stuff, like plain pasta, raw carrots, cucumber, etc...
I worry more because she's a girl, probably, because of the issue of eating disorders. And my dd has said a number of times that she just doesn't enjoy food. Unless it's chocolate of course. That, she enjoys!
The whole issue of food is such a difficult one. I've gently encouraged, cajoled, even bullied her into eating some foods and then worried that I might be causing poor eating patterns, a potential eating disorder, so I can really sympathise with you.
I agree that leaving her to eat for as long as it takes is probably a good idea, stressful though it may be. And it might be a phase, if it's started recently. Peer pressure might be of somehelp, though it doesn't help my girl. I just end up letting her eat less than normal so she doesn't get left out of the pudding course!
Good luck with this singyswife. I hope you find a way to get around this.