Yes you can. Be sure and use the dial ring from the 21j, it will set your stem height correctly. Be sure you donar eta has tall canon pinon, you will need it with the 21j dial ring
Lay the hand upside down on something firm, like a piece of thin cardboard, take a small piece of wood, like a cuticle remover that Im sure your wife uses. Then gently, very gently, roll it up the hand appling soft presure over the bend. Ck it and repeat as much as needed to remove the kink
Yes they will interchange for sure. The only problem you may run into is the height of the canon pinon. Most of the time the canon pinon on the 2824 is shorter than the 2836-2, not always, but most of the time. If you have enough clearance under the crystal with the 2836-2 for the sweep second not to rub, you are good to go.
I don't know if the crystal on your tc watch has a retainer, or if it presses into the case. I have crystals with the lec and I use gen cyclops on my datejust. Im not sure if it would be too much mag on your sub if it uses a retainer, sub gaskets are taller than datejust. If it is a press in, it should work well.
Most gen like constructed case will be waterproof. By that I mean, if you have a crystal that has a bezel that presses over it, most likely it is waterproof. If you have a case where the crystal presses into it, not waterproof. Of course the case tube and crown should be installed properly, and the correct gasket for the back. But, the press in crystal, will most likely leak.