Sugar's Plan Wasn't Very Good (General)

She intended to frame Sheila for attacking Steffy but she broke into Steffy's house unarmed and essentially jumped on a butcher knife. What if Steffy hadn't picked up her knife? What was Sugar gonna do? Also, how did she incapacitate Sheila this long? If Steffy hadn't killed her Sugar would've disappeared into the wind and Sheila would what? Still be unconscious in an abandoned warehouse?

I think that is on purpose to differentiate Sheila vs Sugar further.

I assume there are things we don't yet know, but what if she dropped the weapon outside, and that's why she reached into her pocket?
If her sole focus in life was revenge, when she realized she had no weapon, her options were to come clean and not only go back to prison but also never get her revenge or try to overpower Steffy despite the odds not being in her favor knowing that if she died, Sheila would also die alone in that abandoned building.

Sheila was screaming, so she obviously wasn't incapacitated the whole time. Sugar probably intended to return and let her out. She had to make sure that Sheila didn't have an alibi.

Her plan was probably to release her and then disappear, and Sheila would find herself wanted for murder. And just like no one believes Deacon, they would just put her in a mental ward.

It's been about 10 days. I think most kidnapping stories are like 3-4 days in soap time, though they may last a month on our screens.
10 days is a long time. Whatever supplies Sugar got are probably long gone, and I am sure she has tried everything to get out. She is probably just weak and waiting to die.

when Finn saves her she will be more obseesed with him than ever

DEACON saves her life, not Finn. They have been very clear with the narrative.
And she wasn't bothering Finn before this; Steffy kept showing up at her door, so I don't know what will happen now. I really hope that they move away from that because it is old and tired.

Steffy stabbed Sugar on February 26th. That's more than 10 days

Yes, IRL, but not on the show. Soap time is never the same as real life. You can tell by the outfits how much time has passed. Many of us commented on how long each day was. The stabbing day lasted for almost three weeks of episodes. I think the day Thope broke up lasted 10 episodes. The day of the memorial lasted 6-7 episodes etc.