First re-write-Aspiring writer is forced to choose between his private and professional life when he has to decide if he is willing to expose his mentor for stealing his breakthrough idea after he discovers that his wife is involved as well

What Richiev said about constructing a genuine dilemma is correct.

But loglines are about actions and goals, not about dilemmas. ?Specifically, a logline should be about a goal decided upon, a choice actually made, at the end of the 1st Act. ?The choice may lead to a 2nd or 3rd Act dilemma, but that is beyond the scope of a logline.

So what does the writer do after making the discoveries about his wife and his mentor?

What Richiev said about constructing a genuine dilemma is correct.

But loglines are about actions and goals, not about dilemmas. ?Specifically, a logline should be about a goal decided upon, a choice actually made, at the end of the 1st Act. ?The choice may lead to a 2nd or 3rd Act dilemma, but that is beyond the scope of a logline.

So what does the writer do after making the discoveries about his wife and his mentor?

The problem with this dilemma is that upon reading the logline I don't see any reason he wouldn't expose the mentor and wife who betrayed him.

His wife and mentor betraying him is the reason he should expose them not a reason to not expose them.

Here would be an example of the lead character on the horns of a dilemma:
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"When his mentor steals his breakthrough idea with the help of his unfaithful wife, an aspiring writer must choose whether or not to expose them, knowing his wife could reveal a devastating secret from his past."
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Now we have a dilemma, he wants to get even but first he must neutralize?the chance of his wife blackmailing him with his dark past.