Every time I ride Space Mountain I get bruised somewhere, because being in the dark I can't prepare for drops and turns. After the third time, I said no more.
It was easier before the ride got darker, but it is still not that hard to tell when the relatively small drops are coming. Truly, it doesn't have any big ones.
A few tips:
1. Consider ride length. Ask a CM before you board for ride details. They are happy to tell you duration, max drop, etc. I'm no fan of ride videos before you go, and for many they won't help anyhow.
2. It might help to consider the length of the most intense parts of each attraction. Truly, for BTMRR there aren't any really intense parts. The drop of Splash lasts about 4 seconds. One-two-three-four- you are done. All of RNRC is only 90 seconds. 7D is also rather tame, so of the ones you list, that might be a good place to start.
3. the front section of a coaster is the most tame. If the view from the very front row bothers you, then consider requesting the second row. Though on BTMRR try to front, since you can't see over the front. On Space Mtn, seeing out the front is a bit of an advantage.
If you've ever braved Pirates, the length of that drop isn't much different from Splash. I think the difference is only 10 feet. It is the angle that is a bit different.
4. Aside from advice we can offer here...a single consult with someone professionally trained to reduce anxiety could be beneficial. Something like a session of yoga to learn breathing techniques or a workshop on reducing stress could = learning some great techniques. There are many tried and true techniques out there, but live sessions are the best way to learn them (as opposed to trying to describe a technique here).
5. As others have said, sometimes talking to a (fearless) child helps.