I'd make a well sealed box and put your wood in there with a bucket of water!
I have the opposite problem with humidity and store my hornbow in a plywood box I made with calcium chloride dihydrate, this keep the r.h. at about 40%.
A sealed box is very helpful to control the relevant factors.
1. Yes that would work but is slow!
2. That would also work and isn't quite as slow.
3. See above
4. Hickory would be your best bet but even then 5% is pushing it. A sinew backing would make most woods 'safe' though.
5. Make hornbows