None of the three sentences is exactly right.
"If only" is like "I wish," so all three sentences are not logical since the speaker couldn't want the mother to be heartbroken.
The sentences would be fine like this:
"¢ If only your mother saw the extreme reasonableness of your actions. Then she wouldn't be angry.
"¢ If only your mother could see you now! She'd be so proud.
"Only if" means "only in the event of this circumstance." If the clause with "only if" comes first, the subject and verb in the main clause is inverted:
"¢ Only if your mother saw you right now would she be heartbroken. If you wait until you're looking and feeling better, you can spare her that heartbreak.
If, however, "only if" introduces the second clause, there is no inversion:
"¢ Your mother would be heartbroken only if she saw you right now. If you wait until you're looking and feeling better, you can spare her that heartbreak.