Factors for a comma before subordinate clause?

Hi. I think generally there are three considerations for us to consider when deciding whether or not to place a comma before a subordinate clause. What do you think about the three considerations below? Are they plausible?

1. not quite attached contextually with the main focus (meaning) of the sentence

eg,

He will have no problem making the time for his dinner, provided there is no traffic jam on the way home.



Compare it to this. The underlined subordinate clause part seems to be very much (tightly linked, I might say) part of the sentence and without it (without a comma) the sentence would seem not quite the same.

This contract will be in force starting tomorrow provided that he signs it today.



2. the length of the subordinate clause (that is, if the length of the subordinate clause prevents the correct understanding of the meaning of the sentence.)

I am sorry but don't think I could produce some examples at this moment.

3. the semantic nature of some subordinate conjunctions (for example, the conjunction like "though" which shows a contrast through its usage -- not sure I wrote it correctly to reflect what I wanted to say, though)

eg,

He gives away a lot of money every year, though he sometimes feel financial pinches himself