Hello youngandaglow, thank you for your comments. That Jesus died only for the ones who believe in him is not what this post id about, but the Bible says it several times. It says in Mathew 20:28 that jesus gave his life for many, not for everyone, in acts 2:47 says that "the Lord added to the church the ones who should be saved".
That does not mean salvation is not there for everyone, but God has choosen some to be sav, those who believe in him.
God wnats us to be perfect and we should, however, we won´t in this life, that´s why we need Jesus and the holyspirit to conform us to his image everyday.
God not always heals, there some time he doesn´t want to do it. have you read the book of Job. There are many christian leaders that believe God has given us power over diseases and they themself have died from tumor, cancer, and others.3 john 1:2 is just a wish from the writer fo the letter, nothing more.
The "good news" doesn not have to do much with healing, but with salvation.
Greetings!