I don't think you should be too rigid on your technical values when you play this stuff, or at least there are some things you should consider:
1. roll the weight of your hand over the notes you are playing
This is really what God intended, trust me, you don't want to get carpal tunnel holding down your first finger on that e with your thumb on the g while you are really playing a c. You really don't want to hold anything down, but just use the weight of your arm to keep the string into the fingerboard.
2. Let you fingers collapse, at least sometimes.
You will find that it is very hard to keep them curved. keeping a lot of tension in your hand does not help anything. Rabbath collapses, why can't you?
3. Be creative
Don't worry about playing out of tune, just figure out how you can make this happen, then practice doing that in tune. You may be trying to fit a square peg in a round hole. Don't force it.
Good luck, and post some playing of this stuff, I'd love to hear some.
Thanks