Not sure what sail you have (?), but I find this situation much more likely to occur with the full sail, than with either the mid-vent, or the full-vent sails. I suppose those vents work both ways, but for sure, if the wind catches too much of the backside of a wing tip, it's going to "fold", or flip on you.............
As for your lines, not real sure (based on your post), what you have connected to what, or where? As for your handles, usually, the lower leaders (brake) only have a couple of knots, while the top leaders (drive) may have more like 6 or 7 knots. Most people will actually extend those upper leaders, or replace them entirely with their own, longer leaders.
Based on a standard set of B-series handles, I would normally (personal preference) begin flying, with the brake (lower) lines connected to the 2nd, or last knot out (about 2 "out), and the top lines connected to 6th knot out (next to the farthest out). That still allows for two more adjustments, to increase your brake and dump a bit of wind, should things get somewhat lively, later on. Remember that letting the top line out one knot, is basically equivalent, to bringing the bottom line in one knot (or close) - it gives you one adjustment, to increase the brake. Doing both (top line out one knot & bottom line in one knot) adds two adjustments at once, increasing the brake twice as much (or close). You'll have to determine what is most comfortable for you, but that's a decent starting point...........
Take a look a some of John's tutorials, but specifically key in on where his lines are attached to the leaders.
Happy Flying...............