I read a sign awhile back that said, "Complicated religion is not of God". I truly believe that. The more I ask my JW friends questions, the more coplicated they try to get, even to the point of throwing the original question out the window and bombarding me with unasked for, unneccessary materials. Just the simple facts, that's all I want.
Here is the best, most simplistic explanation I have heard on the subject of grace.
You can't do enough good to earn it. You can't do enough bad to lose it. All you need to do is ACCEPT it.
Accepting it is the key. If you always feel that every gift you've been given has a string attached, then these are not really gifts. If I give my child a $5 bill, he doesn't tell me he can't accept it, because he hasn't earned it. ("Oh, no! I couldn't possibly accept that. Only if you let me mow the lawn. I'll pay you back...) No, way! He knows it is a true gift. He smiles and thanks me, gives me a hug, tells me he loves me! He accepts the gift. More than that, he cherishes our relationship. If he ignored me or disowned me, I couldn't give him any gifts. He wouldn't be receptive. (Yet, I would still love him.)
That's why I think Jesus told us to come to Him like children. They know how to accept a gift.
Don't know if this is helpful to you, but it was very helpful to me. As well as many of the verses you cited. Especially Rom.8:15 and Gal. 4:6. I'm not on the outside looking in. I'm part of the family. I can call God my Father. Just like Jesus taught, and like Jesus did. I never called my earthly Dad by his first name. That was what everyone else called him. I was his child. I had a special relationship with him. I called him Dad. Same deal with God. Through Jesus, I'm adopted, now he's my Dad too. (BTW: My earthly Dad would have been very hurt, if I would have referred to him by his name. He loved being my Dad.)