There is a decent amount of explaining as to how it's better now. Elves have the right to food, water, shelter, a bed, clothes, and the right to consent (or not), and more.
I don't see Cornwall's actions as inconsistent at all. You tried to compare Sui flat out rejecting sex to to Sui flat out accepting sex. It's common knowledge an Elf can say "no" to sex if they want. Had Sui said No to blowjobs, it would have stopped there. Did she want to give a blowjob? No. But she knows her place, she knows what she should do, she's pretty smart about it. She waited for the right time to get out of it, and she did, all while looking like a dunce, increasing the probability of not being invited back to these competitions.
There is a huge difference in action and threats. Cornwall is a master trainer, he got the job because most people think he's
the best trainer. He's definitely not the nicest of guys, he uses threats to train, he scares Elves into submission within Law (mostly). Reminding Sylvia that there are far worst scenarios she could be in is not on par with anally raping her.
It seems you're confusing your desire to not talk to Cornwall with MC and Lin's. Lin actually REALLY wants to prove to Cornwall that she's smart and equal to humans, and that MC loves her as much as she loves him. She was eager to prove herself in both the city and the dungeon event. And yes, Cornwall is an asshole, he flexed his power to get what he wanted. But I see no inconsistencies.
Just a reminder that The Toymaker is not the future of HH, it's a dark timeline.
Nia was originally knocking on the door, the three of them were waiting to drag MC into the car and tie him up (just a reminder that MC is a bigger than average guy, and Elves are kinda small.) But MC didn't go to the door, so she had to resort to plan B. Get the car ready, because she's going in and getting MC herself as quick as possible. She doesn't have a gun, and Syl'anar allows humans to buy guns. It had to be quick and effective.
Nia is very suspicious of humans, especially masters. In the love route, you may be able to convince her to open up