I don't know why he had to have used an ability on the Mother. Just because he was playing with his face doesn't mean he has a Sharingan and used a Genjutsu on her. He 100% did not have Shisui's eye, and I think it would be a little strange for him to have another random Uchiha's eye. Wouldn't anyone notice the eye went missing? A Sharingan is a very secretive eye, they wouldn't let a missing Sharingan go without knowing exactly what happened to it. And I don't think the Third Hokage would just let Danzo have a Sharingan. Maybe he just was always wearing the eye bandages because he knew he wanted to obtain a Sharingan and didn't want it to look weird when he actually got one, this way he didn't have to explain why he has bandages on when he finally obtained the eye.
Same goes for the bandages on his arm. But to refute Floydicals point about him already having Senju DNA. I don't think he has in implanted into his arm yet. For one simple reason, if you look closely the bandages on his arm do not cover his entire hand. He still has half of his hand uncovered. If he had Hashi's DNA in him already, his entire arm, hand included, would look a weird color, and people would notice. So for that, I don't think he even has Hashi's DNA yet. Oh and another reason I just thought of, I don't think he would even have access to Hashi's DNA yet. He obviously got it from Orochimaru, but Orochimaru was still a part of Konoha in this chapter. Oro didn't get Hashi's DNA until he defected and robbed Hashi's tomb when the Third Hokage came to kill him.