@1 Momoshiki was going after sasuke with intent to kill. Hence the more aggressive attacks with the lava, chain, hammer . . . He wanted to capture naruto to absorb his chakra which he stated multiple times.1. Or Naruto was allowing him to keep up? There is no I in team remember that. For example when naruto and sasuke both tried to kick sasuke and he knocked sasuke away with his chakra chain and hit naruto with the giant rock. That's team work. Without team work they would've lost. Just like how they fought kaguya and madara and obito with team work
3. I don't think he can. It took all of Naruto's chakra to contain the blast, and he still got captured. And we all know naruto has chakra several times higher than Sasuke's. There hasn't been feats of Susanoo being manipulated like that. Besides, if Sasuke could do that then why didn't he wrap Susanoo around Kurama which would've doubled the protection and saved both of them?
Yes they would have lost without teamwork, but that's because they were nerfed. Sasuke barely used any rinnegan jutsu. Naruto has some pseudo RSM cloak. With his full power sasuke would take momoshiki. He'd absorb every jutsu he uses, which includes the bijuu dama that exploded in konoha. Susanoo slices him in half as shown in the boruto movie.
@3 Sasuke knew Naruto had to bait the enemy so everyone else would be safe. He already told naruto they couldn't use their full power else they would drag everyone into the battle.
Also susanoo's form has being changed before to fully cover the kyuubi. What's to say the form can't be changed to accommodate a different situation?