Why does the author use ‘would’ in “I would kill him inchmeal just now”?

Solution 1:

From a letter by Charles Lamb (1775-1834). As well as "a short while ago", "just now" can also mean "at present or at this moment", which would fit the context. This useage is very common in Scottish speech.

a. very short time ago
b. at this moment
c. (South Africa informal) in a little while

Just now (Collins Dictionary)