OR:If it were you, you would
havekick edhim off the chair.
If I were you, I would
have torntear Mr.X into pieces.
You have hit on the meaning of the 'if' clauses which are in the subjunctive, but you cannot replace the verbs with the phrase you have suggested.Can we replace the red letter words with a phrase 'is in the place of'?
Re: If it were you, you would have kicked him off the chair.
Once you put yourself in the other person's "shoes" then it's best to say what YOU would have done and not what the other person would have done. It's a bit hard to explain, but suffice it to say that you shouldn't use "you" in both the subject and the predicate since you're hypothetically putting yourself in someone else's place to show how YOU would have handled the situation differently.
Hope that's more help than confusion!