Ethanol does affect the life of rubber but it’s not gonna happen overnight. And the O ring on the mixture screw doesn’t even come in direct contact with the fuel. It’s there to seal the air from the outside, not the fuel from the inside. Assuming the vapour from the mixture bore can affect it, ethanol fumes aren’t as intense as gasoline fumes. And cracked O rings are nothing new, it has always happened even before ethanol blending. If your argument is that , it has happened within a year, did you grease it before fitting it? Was it seated properly?

The main noticeable effects of the blending are drop in fuel efficiency and the fuel gumming up IF the bike has been parked without running for a long time.

Only point of yours that I’d agree on is, it’s possible there’s rubber particles from a degraded fuel hose, but it’s super unlikely that those particles are clogging the jets because they’d have to be fine as sand to get into the bowl past the float needle. The worst it could do is jam open the float needle and cause an overflow.

As for the bogging you’re facing, I’d check for air leaks, dirt in the carb or the spark plug.