It looks like taking the 850 and running might be the best advice.

When I ran some options looking for something that would work for you, I can't even find OSL-any us gateway airport for less. Throw in SVG being a regional airport (though not at all small), and PHL being a fortress hub for US, and there are lots of things working against you.

Off-topic, but I absolutely adored your country. Expensive to visit, but hands down the nicest people I've ever had the pleasure of interacting with in my travels. Preikestolen was absolutely worth the hike, would have loved an extra day to see it by boat from the bottom of the fjord. Some of the most stunning scenery anywhere.