I will have to reread
Leaf by Niggle,
Esty, before I can reply at length here to yours and
davem's discussion, but for a Catholic statement on purgatory, here is a link to the
online Catholic Encyclopedia.
Possibly an entry closer to the teachings Tolkien would have received (and we should beware the automatic assumption that he held no independence of thought concerning the theology he was taught) would be found in the 1911 edition of the
Catholic Encyclopedia, which expresses Church doctrine and ideas before the reforms of the Vatican Council. That, of course, is not available online but only in libraries. Fascinating reading at times, especially in comparison to later editions of the encyclopedia.