Re: your second point, there actually does seem to be a pretty negative correlation between working hours and GDP in the OECD statistics you link. Just sort on the average-hours-worked column and look at who's at the top and bottom: with a few outliers, the rich countries are all on the low end, and the poor countries are on the high end. The shortest hours are in the Netherlands, Germany, and Norway; while the longest are in Mexico, Korea, and Greece.

This doesn't establish that longer hours lower GDP, of course. If I had to guess on a causal direction, it'd be some mixture of [more GDP] -> [shorter hours], as well as a good helping of [better-run country] -> both shorter hours and more GDP.