Thank your for the motivation, the sad part is that I REALLY do want to go! I've never been in tower of terror and I will never be on it again if I miss this. I guess it's better to keep my ears safe though...
Just saw this. If you really want to go as you put it then go! My opinion is probably not gonna be agreed with here, but I don't think Disneyland is what I'd call 'dangerously loud'. It's not in the realm of a rock concert for example. Ear plugs or muffs will protect you on that front. As far as your eustachian tubes go, why not try out a mid sized ride and see how you do? I don't think you will have any issues personally, but I'm in no place to say this for sure. If for arguments sake you do have an issue then just avoid all rides that are similar. There's plenty of other rides/stuff to do such as the simulator rides and stuff.