HP: BR, you raise good questions but there are more questions than even the ones you mention that need to be asked. It is commonly indicated that grace is that which is needed to bestow the ability to act in a manner pleasing to God, as if man is born without the necessary abilities to do what He commands. This makes God out to be a taskmaster, sowing where He denied to endow or bestow the very abilities to carry out the commands He has stated He will punish man for the failure to comply with. I maintain that grace is not the bestowing of abilities, but rather it is offering man a pardon for willful transgression of known commandments of God when and only when man could have obeyed but did not.
My intent in this thread, is to illuminate the clear distinction between justice and grace that so many confuse. It would be mere justice for God to bestow the needed abilities to obey His commands not grace if God is going to praise or blame me for their intents. That is the point I have in mind.
If man is born in such a state as you claim, i.e., sinful from birth, how is it grace, i.e., ummerited favor, for God to bestow upon man the needed abilities to obey?? Would it not be justice that if man had no other possibility than to be punished for failure to carry out His commands, that God would grant to such creatures the ability first to obey? God did not only mete out punishment for Adam, but us as well. Why would God not be required by justice to provide us with the same abilities requisite for obedience as Adam?
Scripture clearly states that the children are not responsible for the sins of the parents, but everyman is responsible for his own sin. To blame a man for something he had absolutely no role in nothing short of injustice. God is Just.
Subsequent to salvation, I believe God indeed enhances our abilities to obey Him via needed motivation. This is indeed unmerited favor or grace. I would call it grace upon grace. Not only does He pardon our past sins, He comes along and upholds us with Divine motivation to continue in obedience. There may at times be a fine line between grace and that which in a sense might be called ability, but when you eliminate the part of man's will being fully capable for first light of moral agency to obey God's demands from the mix, you end up with nothing short of God being a Divine respecter of persons. If some are granted the abilities but others are withheld the needed abilities to obey, nothing is just concerning their fate.
If man is going to be blamed or praised, they must of necessity have the requisite abilities to obey. The granting of abilities is not grace, it is justice.