I've never had a wheat beer take longer than 5 or 6 days to finish fermenting, and the few times I used Coopers kit yeast on any beer it was also done in under a week. And even though 1056 is a pretty high OG, it should still finish down towards 1013. I'm guessing your very long lag time and a 1019 reading after 13 days is suggesting you have a yeast problem....probably not enough healthy yeast given you used the kit yeast from under the lid....which is both small and not handled all that well. Do you have any other yeast on-hand that you can use to finish this brew off?
If you can be bothered, you should try a forced ferment test....draw say 250ml out of your fermenter, put it in a sanitised jar and keep it somewhere warm, as close to 30C as possible. Shake it often over 48 hours, then measure the gravity. If it's still 1019 your yeast is completely dead, and you'll need to add fresh yeast to your fermenter. If the samples' gravity drops to the expected FG, it's just a matter of patience with the main batch (and occasional gentle swirling).