Right under the LPA, your hubby can make payments for people for whom your FIL is reasonably expected to provide. Thus he could buy new furniture for the wife, but as has been said above, she has no absolute right to it.
Once FIL dies, the LPA ceases immediately and has absolutely no effect. It has been pointed out above that the wife can make a claim for reasonable financial provision under the Inheritance (Provision for Family and Dependants) Act 1975. Her claim will be on the higher standard (the spouse standard) which is "reasonable financial provision whether or not required for maintenance".
I can't possibly say whether she would be successful without knowing all the facts, but unless she is wealthy in her own right, I suspect the Court may make some additional provision. What will be significant in this case is the length of the marriage (28 years). Chris has set out all the factors in his post. However, there is an additional factor - the "deemed divorce" test. Ie would would the wife have received if the marriage had ended in divorce rather than death.
If after FIL dies she intimates a claim, your hubby needs to seek legal advice ASAP from a specialist.