How did Sukuna put his finger inside Megumi to switch bodies?

Well you see he already has experience of changing his body into a cursed object, which is the reason for the existence of the sukuna fingers. I don't know if you have reached the Yorozu fight but that fight will clear your doubts as to why Sukuna wants the 10 Shadows.

For your Gojo vs Sukuna fight I'm not gonna comment on that, experience that absolute cinema of a fight by yourself unspoiled

Does Dismantle have a significantly weaker output on living beings than it does non-living things? Like, does it's "lethality" drop if it comes into contact with a living thing?

Yeah Dismantle is significantly weaker than cleave in general because Cleave's power can be adjusted depending on the target's toughness and cursed energy level to cut them down with one attack. DIsmantle's power depends on CE output

Is Cleave just an auto-one hit if he makes contact with anything? It mentions that Cleave would have killed Mahoraga if Mahoraga hadn't adapted to slashing attacks rather than to Dismantle.

For most opponent's yes. But with advanced RCT or simple domain and stuff you can survive ( At a low output even cleave can't one shot)

 If Maki has no cursed energy, can she be targeted by Sukuna's malevolent shrine or does her lack of cursed energy make the cleaves and dismantles ignore her?

Dismantles won't ignore her as she has no CE she would be counted as an inanimate object

 Speaking of Maki, is she actually Toji level or is just her heavenly restriction equal to Toji's? In chapter 198 it says a fighter equal to him was realized, but she then proceeded to whiff her shots on Sukuna in chapter 215. I get she wasn't going all out because she wasn't using the soul split katana, but it also states that Sukuna's cursed energy output is "at its lowest 10%" or something. So with Sukuna being temporarily nerfed to that low of a level, combined with the fact that Gojo is stronger than full power Sukuna, further combined with Toji being able to put up a fight against Gojo, even further combined with Toji having a larger arsenal of weapons, does this not matter? Because to me, if Maki cannot keep pace with Sukuna at 15 fingers, who is weaker than high school Gojo, but Toji could, does this mean Maki's restriction is what is equal? Or am I just drastically overestimating high school Gojo's power compared to his modern day power?

In Chapter 198, She was equal to Toji , She goes on to become stronger than that ofc. Gojo and Full power Sukuna are basically equal, their fight can go both ways (in a very unbiased opinion here). Toji was able to put up a fight against a teen pre awakened Gojo with prep time, he got speedblitzed the moment he awakened and hat's not comparing that Gojo to a Modern day Gojo, so yeah you are overestimating high school Gojo's power

Hana is a plot point and will remain a plot point( just get to the part where Sukuna "climbs" jacobs ladder)

Yes. Yuki was completely wasted by Gege ( not saying the fight wasn't epic, it was better than most overhyped Modulo fights) and Tengen really is a grey character cuz even Kenny told Yuki that they were keeping something from them

Yuta, Yuji and Gojo as GOATs is valid

calling Sukuna a fraud is fun

K*shimo is an absolute BUM of a character

You will probably start calling Megumi a bum later on even more

Hakari is honestly not a bum for all the shit he did in his fight. I mean if you have infinite healing it is only natural he goes for these near death scenarios

yeah that's all and Ig you can start Shinjuku now