No, that is irrelevant to the case at hand. If Obama is judged to have failed to qualify, then he was never President, so XXV does not apply. It is illogical to remove from office someone who was never legally in office.
XX Sec 3 applies directly.
You are completely wrong. The election happened and the administration was sworn in. You don't get a do-over on that. If it is found that Obama deliberately lied about his qualification in order to become president then he'll be removed. But the 25th Amendment kicks in, not the 20th.