I just wiggle that up and down and pull backward and down. Same if you separate the inner fairings from the side pieces. Take out the fasteners ad wiggle until it lets go. It is a beotch to get the side fairing separated from that point on the top cowl. Also the ram air covers are tricky to get to mate up. The belly pan is not easy....they all suck!
Just be careful. I've done it at least 20 times and it's still quite a task. Be careful and don't force anything.
I had that happen on a drain plug. I used a chisel to carefully split it and I pried it apart with a screwdriver. I wouldn't thread it off if it is tight. If that is an OEM crush washer, it's pretty delicate but it might be a lot stiffer if it's completely flattened.
I suspect your drain plug was either overtorqued or the washer was used more than once. Normal torque should not cause the washer to expand onto the threads like that. I use 12 ft lbs and I have used the same washer repeatedly because those things are so hard to come by at a shop. I just reused the one I've had for at least the last 3 oil changes and it came right off. It looks like it did seep a bit under the oil pan but not enough that the oil level went down all summer. I reused it again because it's all I have. Don't overtorque. Do use a new crush washer if you can find one!
I guess a solid aluminum one like Kawasaki is also exceptable for use on the busa.