I'd fly with that engine and I'd be tempted to push it along for another ~90h which would be a lot of flying. As long as you don't run it until it disintegrates......
Despite rotax discontinuing the 618 there is still good parts availability. Can still buy a new crankshaft ready to drop in for $1500. A rebuild is usually 3/4 that amount.
Two-strokes can be ornery at times but for the most part they are easy to maintain.