The threshold for sound mind is a little more stringent for an irrevocable trust than for a revocable trust or a will. As with will contests, a trust contest is typically a full-blown legal proceeding involving a trial. Breaking the trust would ultimately come down to the opinion of a judge.
A quid is a slang term for an english pound (currency not weight). Bob is slang for an old english shilling. Currently it's 100 pence = one pound. A shilling would be now worth about 5 pence today. It used to be 20 shillings made a pound.A shilling was 12 pennies.
The slang term for a pound is a quid and there are other slang terms for various amounts of money that a reader will come across in historical novels. A monkey is 500 pounds, a pony is 25 pounds. You will often find those last two terms bandied about by gamblers in regency novels.