Wow, Tom! you are ambitious. looks like you'll have a lot of fun.
Do you have a way to fabricate parts, machining, welding, etc?
I can tell you I started with similar skills about 1 year ago and have progressed some but nowhere ready to tackle something as big as what you are doing. I bought a few reference books...my favorite so far is Electrical Engineering 101 by Darren Ashby. This book plus what I have learned online and from Electrical Engineers in my office.. .is what I have to go on so far.
My guess is that your cordless screwdriver will not come close to the torque you need. sorry.. i am trying to think of an alternative and nothing comes to mind immediately. I think you would want to do a lot of research before committing to which parts to use.