I have 600 hours on my original plug wires and don't plan to change them soon. Before I change plug wires I would try unscrewing the boots and clipping of about 1/4" of wire and reinstalling the boot. It often solves ignition problems.

You really should be continually monitoring the Rotax-Owner website and read the forum posts on a regular basis. Nearly all the questions you have asked have been discussed many times on the forum, including my suggestion of clipping the plug wires. Any Rotax owner doing his own maintenance should be reading that forum. That website also announces each new service bulletin as it comes out, like the one recommending against the Evans coolant. A Rotax repairman who doesn't keep up on service bulletins would be highly suspect in my opinion.