Is there anyone with legal knowledge able to throw any light on the circumstances in a set of deeds I've been puzzling over?

In 1890 Thomas passed his promissory note to Mary, a neighbour, for the sum of £10 bearing interest till paid at £4 10s per centum per annum. Thomas died in 1897 intestate and letters of administration were granted to his son Richard, who died in 1903 without having fully administered the estate. The sum was still due in 1909 and owing interest from 1900. Letters of administration 'de bonis non' (?) were then granted to John, another son, and on the 24th May1909 John, Robert (another bachelor son) and a third person were bound in the sum of £300 on condition that John make or has made an inventory of the estate. They all signed with their X mark.
A month later John is in the Bankruptcy division of the high court 'having become embarrassed in his circumstances' and transfers to an accountant the whole of his real and personal estate, including a farm and a croft, for the benefit of his creditors. The next month, July, a high Court Summary jurisdiction granted execution in favour of Mary for the sum of £8 10s, plus costs, and she also obtained execution against John for £120 plus costs, and a judgement against him for £40 10s plus costs and a further execution against him as the administrator de bonis non of Thomas for £10 plus costs. This was all placed in the hands of the coroner who proceeded to sell the farm for £1850 which was enough to cover all debts and so John was given back the croft. The amount raised by the sale of the farm (bought by a Douglas JP) seems so much in excess of what was required to pay the debts I wonder why the croft wasn't sold instead.

Is it likely for bankruptcy to be caused by being an administrator (is that the right term?) of a will?
Mary's claims can't all be due to the promissory note, can they? There don't seem to be any other documents concerning further loans.
What would lead to the bond being as high as £300? I wonder if they knew what they were agreeing to as all were illiterate.