If I do find a pot big enough how long should I boil the wood?
Until it sinks! I wish I could do better than that, but some of my small pieces have taken 2 hours or less, others more like 10 hours.
Also, cannot speak for others, but boiling driftwood STINKS, IME
! If you can do it outdoors (Gas grill, camp stove) you'll be more popular with your significant other. Also, When I've boiled mine, I weighed it down during boiling too, used a couple rocks. Please be safe doing any of this, don't burn or scald yourself, or burn the house down. Pay attention to it, because you will likely need to add more water a few times during a long boil.