The drop in the dark on Splash Mountain, IMO, is worse than the "big drop" on Space Mountain.
The "big drop" is at 1:53 mark in the video
https://www.youtube.com/watch?v=OndqlhVJ0HY
The "big drop" is at 5:07 mark in the video
https://www.youtube.com/watch?v=0MEo8XJiPhg
Indiana Jones does not have any drops, so you have nothing to be worried about there. The only part of that ride that could remotely be considered a drop is at the end when you encounter the rolling ball and then going under it.
And that part of the ride is taken at such a slow speed, you hardly notice you're going down hill.
As for the butterflys in your stomach feeling, well everyone is different. I rarely get that feeling anymore when I go on theme park rides (been on over 100 roller coasters). And when a ride gives me that sensation, personally, I like it! None of the rides at Disneyland or DCA give me that feeling.
Thanks so much for this!