Sorry about the Inverted Scale... didn't get that last zero in...
The thing that pops out at me... just leaps out at me... is how you allow BB to control your happiness, your purpose and your decisions. For a moment there, when you were talking about airstreams... you sounded a bit like CeMar...
Where I see you falling flat on your face is not in knowing what would make you happy, what you would do, or how you would get there... but that you don't deserve it, somehow.
All the things you say you'd like to do.... I was going to suggest to you in one form or another... but it would fail, because you won't DO them. That is not a criticism. That is now The Goal.
Meaning... you are going to have to practice disappointing BB and allowing her to take care of herself. You have debilitated her, in a way, by always coming in to rescue her. In essence, you are dealing with a spoiled, petulant child, and you have contributed quite a great deal to her state.
That's nothing to be sorry for... it's just something to change... IF you are willing to take control of your own ship (your own life), and in so doing, help make hers richer as well.
I'm serious. One of the reasons she doesn't GO ANYWHERE or DO ANYTHING is because she knows she controls this part of you and your R. At least on some level. If she goes with you, or does anything with you... it upsets the balance of the R, and she loses her power. I'm sure you even help her do this by saying things like... "Would you like to go do x with me? You don't have to if you don't want to." And YOU do this, because in actuality, YOU are the one who is controlling the R.
On a scale of 1 to 10, 10 being the most, how stressful was it for you visiting your sister? Because of the stress you felt, how likely is it you will repeat the trip?
You want BB to change so you don't have to feel bad, stressed, lonely, etc. You use your energy trying to change her to get the life you want. The minute you stop doing this, she grabs for you, because it is a life she is used to as well.
And because you are giving up all these other things you would like to do (and you've got quite a list there), you work. It's the one thing you can do, that gives you some sort of pleasure on some level, that even SHE can't ruin. Though it does get you out of the house and serves her purpose in some way.
So. What all this boils down to is... how bad do you want to take charge of your own life, and let your purposes and passions define you, instead of a lifetime of habit? You are so convinced that IF you change you are going to hurt BB or end your marriage, you stop yourself before you begin. I hate to tell you... there is no possible way you could know this. You just think you do, based on early warning signs you have NEVER moved beyond.