Increasing damage during damage step don't stop the attack. So yes, increasing Cyber tutu this way work.
Leaving a monster in def position don't work, as the ATK count, not its position. But I don't know how set monster work(likely they count as '0 atk' ones.
You can easily test those things against LDs.
I meant to say that it stopped working if the monsters were set facedown, and that is usually what people ended up doing to me in pvp to stop her. She is not good for furhires since they have recon and donpa, and beat a lot and are swarming the board a lot and if your deck has only direct attack monsters, it is hard to clear the weaker furhires with just s/t thanks to wiz.
Another problem is that if you have a bunch of stuff to juice her up for the damage step, then you have less cards to protect her and if you don't get what you need all the time, it is hard. With 4000 lp back and better cards, I do want to revisit this deck idea, but I want to try to get powerful rebirth for her and the others.