Tobi can't phase through Shinra Tensei, Banshō Ten'in, and Chibaku Tensei

[Kira was Righteous]

Shinra Tensei-Yes

Banso Tenin-No i have my reasons he could phase if Pain tries to attack but not the actual move

Chibaju Tensei-He couldn't attack as he would get sucked up into the sphere where he would keep phasing and unphasing until he dies.Gravity>Tobi

 

[neowisdom]

after re-reading the scene, i would say at this point

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he committed to Izanagi, after learning that she knew the limitations of his technique and he knew the sheer extent of hers , he felt like it was the route that warranted the least amount of risk,especially after she blew his arm off demonstrating she had a solid understanding of his techniques, its clear here

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that konan spent countless hours analyzing the techniques she knew about, mainly his intangibility, and s/t technique,and would probably have a contingency for the event that he tried to escape through the method you mentioned, i believe he simply chose a technique that she didnt realize he had to surprise her, thats all,

edit: so basically im saying initially he fell because he was trying to use his s/t transfer, he was materialized and gravity did its thing , then realizing he couldnt use his s/t technique, and went immediately to izanagi , which he has perfected, which she wouldnt expect

I don't know if this is going to change your opinion but I thought I'd point it out to you. About what you said in your "edit" at the end: Tobi was actually falling while the paper bombs were moving through him so that means that gravity did affect him while intangible.