The sentence implies that it was plain to see that the director was bored by his cast and their performance, and they had a hard time tolerating (suffering) his display of displeasure. They were not exactly “accepting” of his attitude, which is why saying so would be far from/belittle the truth, an understatement.
If you are at the receiving end of something unpleasant that you tolerate or put up with (willingly or unwillingly), you could be said to be suffering it.
Examples: I suffered fools so gladly. (Line from Drowned world/ Substitute for love – Madonna)
The : you mention is a colon.
A colon may be used between independent clauses when the second sentence explains, illustrates, paraphrases, or expands on the first sentence.
Example: He got what he worked for: he really earned that promotion.
In your example, both the sentences before and after the colon can stand on their own. However, the second sentence elaborates on the first, which makes the placement of the colon legitimate.