FWIW, This is what I do
I burn 90 octane zero ethanol about 70% of the time. I add octane boost to the fuel to get it to at least 91 octane, which is the minimum recommended by Rotax. In the Midwest, it's about all you can get.
When flying cross country, I will divert to get auto fuel if it's available but I'm okay with burning 100 LL if nothing else is available. I always add Decalin to the fuel to help scavage the lead out of the engine. I burn this about 30% of the time. When I do, I change the oil more often because I can see the difference in the oil when burning 100 LL.
Currently, I'm burning Shell 93 octane V-Power with up to 10% ethanol. I have a tester and I've never found the ethanol at 10%. It's usually around 7%. I've grown a little tired of all the mixing of additives so I'm thinking of just going to premium auto fuel from this point forward.
Bottom line is that I always carry a bottle of octane boost, a can of Decalin, and an ethanol tester with me at all times. I bought a water-tight case from The Container Store that I carry in the baggage area.
What I get from the material on the Rotax owners site is that it's okay to burn E10 in the Rotax. In fact, it's preferable to burning 100LL. Lead is bad for the gearbox and valve guides so if you can avoid it, you should. By the same token, you shouldn't be paranoid about burning it if it's all you can find. Just use a lead scavenger. Another pilot on my field burns a mixture of 90 octane E0 and 100LL, obstensively to get the octane rating up. To me, it's the worst of both worlds and I had no interest of going down this path.
This is what I do and I'm comfortable with my decisions up to this point.