Yes absolutely right we aren't under the ceremonial law and as Galatians 3:24 says-Wherefore the law was our schoolmaster to bring us unto Christ,that we might be justified by faith.
Even tho v 25 says we are no longer under a schoolmaste,but, through godley sorrow which leadeth to repentance to salvation(actually being born again) and worldly sorrow leads to death and we know what happened with Judas Iscariot who repented unto himself and not towards God.
Please correct me if i'm wrong,but everybody who committed suicide in the Bible
Abimelech,in Judges,Saul,in 1 Samuel,Saul's armour bearer,in 1 Samuel also,Ahitophel,in 2 Samuel,Zimri,in 1 Kings and of course Judas Iscariot were definately not godly men and were wicked?
1 Corinthians 3:17 also says-If any man defile the temple of God,him shall God destroy;for the temple of God is holy,which temple ye are.
It's obvious that anybody who does commit suicide think that they have no hope and no way out,but the Lord Jesus Christ is a believers blessed hope and he always gives us a way out.I too went throgh a number of yuears of bad depression a number of years ago when my sister committed suicide and praise the Lord Jesus Christ i didn't do the same when coming close to it.As you said even a non believer knows it's wrong,so how much more someone who is saved and indwelt with the Holy Spirit?