...would not come... - he had made a decision not to come
...was not coming ... - one or other of the above two, and he's not saying which (either for 'political' reasons, or just because it's not relevant - what matters is that he's not going to come)
He would not be coming - 'I won't be coming - I'm baby-sitting that night.'
We would not come - 'I won't come. I can't stand her friends.'
He was not coming - 'Give my love to Sally - I'm not coming tonight.''
The second (that is fourth) sentence does express a condition, but the condition refers to his state of mind (his choice); there's heavy stress on will.
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