"Blen" is probably "Blain" -a boil or blister, or the scar thereof. By extension, the disease that caused it.

"The hole in his boozen" might be "The whole on (i.e. of) his bosom", but I'm only speculating there, not having heard the recording.

"Closin(g)" can mean "breathing with difficulty".

The first verse is quite heavily Scots, while the rest are a lot more like other versions I've come across; I wonder if they've collated more than one set? Does it say anything in the sleeve-notes?

Malcolm